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111th Session.] 

FRIDAY, APRIL 28, 1865. 

[No. 64:9. Vol. XIII. 

tj^bijE of contents. 

Announcements by the Council : — Ordi- I 
nary Meetings — Cantor Lectures Page 387 

Proceedings of the Society : — Twentieth j 
OrJdnary MLecting— " On the Wear and 
Tear of Steam Boilers," by Frederick i 
Arthur Paget, Esq., C.E 387 I 

Discussion 398 j 

Dublin International Exhibition 400 ; 

The Paris Exhibition of 1867 401 

Fine Arts .-—Paris Exhibition— Photo- 
graph of Dante 402 

Manufactures :— Tuscany Straw Work-- 

Galvanic Pile 402 

Commerce :— Stagnation of Commerce .. 402 
Colonies : — Colonial Societies — Acclima- 
tisation in Victoria 402 

Notes : — Danish Industrial Exhibition — 
Hydraulic Works in the Doubs— Au- 
tographic Telegraph— Gas Lighting 
in Paris — Lenoir Gas Engine . ... 403 

Correspondence : — City Horticulture — 
Photography on Painting Canvas ... 403 

Meetings for the Ensuing Week 404 

Patents 404 


Ordinary Meetings. 
Wednesday Evenings at 8 o'clock. 

May 3.—" On Colonization ; its Aspects and Results." 
By William Stones, Esq. 

May 10. — " On the Art of Laying Submarine Cables 
from Ships." By Captain Jasper Selwyn, R.N. 

Cantor Lectures. 

The Third Course for the present Session, con- 
Bisting of six Lectures, " On Some of the Most 
important Chemical Discoveries made within 
ihe last Two Years," by Dr. F. Grace Calvert, 
F.R.S., F.C.S. (Corresponding Member of the 
Eoyal Academy of Turin ; of the Soci^t^ In- 
dustrielle de Mulhouse ; of the Soci6t6 Impe- 
riale de Pharmacie de Paris, (fee), is now being 
delivered on Tuesday evenings, at Eight o'clock, 
as follows : — 

May 2nd. — Lecture 4. — On the Discoveries in Phy- 
siological Chemistry. 

May 9th. — Lecture 5. — On the Discoveries in the 
Chemistry of Rocks and Minerals. 

May 16th. — Lecture 6. — On the Discoveries in the 
•Chemistry of Metals and Alloys. 

These Lectures are free to Members (without 
ticket), and every Member has the privilege of 
admitting One Friend to each Lecture. 


Twentieth Ordinary Meeting. 
Wednesday, April 26, 1865 ; Peter Graham, 
Esq., Member of Council, in the chair. 

The following candidates were proposed for 
election as members of the Society : — 

Bean, Alfred W., Danson-park' Welling, Kent. S.E. 
Dent, William, 21, Newcastle-street, Strand, W.C. 

Gover, William, Italian-villa, Lee-road, Blackheath, S.E. 
Hancock, C, 6, St. Germain's-villas, Lewisham, S.E. 

The following candidates were balloted for 
and duly elected members of the Society : — 

Bourne, Geo. S., R.N., Royal Hospital, Geenwich, S.E. 
Brackenbury, Capt. C. B., R.A., 1 Adelaide-place, Wool- 
wich-common, S.E. 
Brady, Francis, 12, Limes- villas, Lewisham, S.E. 
Brumleu, Charles, 6, St. John's-road, Brixton, S. 
Burt, C. J. T., Roadside, West Hill, Putney, S.W. 
Clark, Edward, 2, Rose-villas, Montpelier-road, Peckham- 

rye, S.E. 
CoUerill, W., Norbiton-park, Kingston-on-Thames, S.W. 
Damby, Thomas, 7, Parliament-street, S.W., and 31, 

South-grove, Peckham, S.E. 
Dolan, H., Park-hill, Clapham, S. 
Eden, Frederick Morton, Capel-house, Kew, W. 
Farnall. Harry Barrard, Poor Law Board, Whitehall, S.W. 
Field, Hamilton, Clapham-park, S. 
Folkard, Augustus, Haslam-house, Lewisham, S.E, 
Gibson, John, 1, Era-place, Surrey-lane, Battersea, S.W. 
Goodwin, Rev. Thomas, M.A., Croom's-hill, Greenwich, 

Gowan, George D'Olier, Wood-lawn, Dulwich, S.E. 
Graham, John, 74, Manor-street, Clapham, S. 
Harker, George, Uplands, Sydenham, S.E. 
HaiTison, C. Wrightman, Pneumatic Loom Company, 

26, Lombard-street, E.C. 
Hawley, Henry J., 4, Foxgrove-road, Beckenham, S.E. 
Herapath, John, Catford-bridge, Lewisham, S.E. 
Hills, F. C, Denmark-hill, S. 

Hoblyn, Thoa. Hallam, Rick ling. Bishop's Stortford. 
Hollo way, William, 4, Park-road -villas, Battersea, S.W. 
Hosegood, Thomas W., Rosend ale-villa. West Dulwich, S. 
Jerram, E. J., 3, Cedars-road, Clapham-common, S. 
Johnson, John G., Assay-office, 18a, Basinghall-st., E.C. 
Legg, George, 61, King William-street, E.C. 
Lewis, Thos., Somerset-lodge, 35, London-rd.,Croydon, S. 
Lord, W. B., R.A., 37, Stockwell-park-road, Brixton, S. 
Macandrews, J., Roeharapton-lodge, Roehampton, S.W. 
McArthur, W., 1, Gwydyr-houses, Brixton-rise, S. 
Martley, W., 15, Cedars-road, Clapham-common, S. 
Menge, R'-v. J. P., Electiical-hall, Park-villas^ Lower 

Norwood, S. 
Milnes, William S., 11, Devonshire -road, Greenwich, S.E.. 
Monk, J. C, 3, Manor-road, Wallington, S. 
Moren, George, 38, Threadneedle-street, E.C. 
Painter, Henry, 1, Arlington- villas, Lougbborough-parfc, 

Brixton, S. 



Papengouth, Lieut. Oswald C, 12, Blootnsbury-sq., W.C. 
Price, Charles J., Carlton-chatnbers, Regent- street, S.W. 
Tefft, Benjamin F., LL.D., 31, Upper King-street, Hol- 
born, W.C. 

The Paper read was — 


By Frederick Arthur Paoet, Esq., C.E. 

According to the published report of the engineer of 
the ivlinchester Boiler Assurance Company, forty-three 
explosions, attended with a loss of seventy-four lives, oc- 
curred in 1801 in this country- The engineer of the Mid- 
land Boiler Assurance Company gives the number as forty- 
eight, causing the deaths of seventy-five and the injury 
of 120 jicrsons. These statistics are confessedly incom- 
plete, being, from obvious causes, numerically under- 
stated. Tue Royal Commissioners on the metallic mines 
report that, in the districts of Cornwall and Devon, boiler 
explosions are of very frequent occurrence ;* and, in these 
sparsely populated districts, they easily escape the public 
attention. Explosions, again, which only injure without 
killing outright, and therefore do not call for a coroner's 
inquest, also happen without attracting much notice. The 
figures cited thus understate the destruction and injury to 
life through boiler explosions, while only a guess can be 
hazarded as to the annual lots of property they cause. 
Each explosion testifies to the probability that a number 
of boilers have been prevented from exploding by mere 
chance, as also to much unchecked decay and deteriora- 
tion, which might have been prevented by greater care 
and more knowledge. Besides, apart from the disas- 
trous results of an explosion itself, the undue wear and 
tear of boilers means the suspension of the workshop or 
factory and the demurrage of the steam-vessel. With 
respect to the causes of explosions themselves, " there 
are," to use the words of the late Mr. Robert Stephenson.f 
" but few cases which do not exhibit undue weakness in 
some part of tlie boiler ; " and the same opinion appears 
to be held by Professor Faraday .J The opinion thaft an 
explosion is rather due to the weakness of the boiler than 
to the strength of the steam may in fact be said to be 
universal. There is, indeed, a very complex train of 
mechanical, chemical, and physico-chemical forces, lead- 
ing to the deterioration and consequent destruction of a 
steam-boiler, and it is probable that no other metallic 
structure is subjected to such complicated conditions. 
The pressure of the steam and the heat of the fire produce 
mechanical effects, while both the burning fuel and the 
water react chemically on the plates and in accordance 
with their varying chemical properties. Each of these 
agents play, so to speak, into the other's hands, furthering 
and quickening the other's progress. It is difficult to 
distinguish with strictness between the effects of each ; 
and it is mainly for the sake of convenient examina- 
tion that they can be classified into : — 1. The effects of 
the pressure of the steam ; 2. the mechanical effects of 
the heat ; 3. the chemical eflfectfl of the fuel ; 4. the 
chemical effects of the feed-water. 

TjiE Direct Effects of the Pressure of the 

In calculating the working strength of a cylindrical 
boiler, the plates are assumed to be under a static load, 
and to be submitted to a tensile strain. The former 
of these assumptions is seldom, and the second is never 

* Report of the Commissioners on the Metallic Mines. 
Presented to both Houses of Parliament by command of Her 
Majesty, 1864 , p. xxi. 

t Proceedings of the Institution of Civil Engineers, 1856, 
p.281. • 5 , » 

I Proceedings of the Institution of Civil Engineers, 1852, 
p. 392. ^ 

correct. There are two principal causes that tend ta 
exert impulsive strains on the sides of a boiler: — 1. 
The sudden checking of the current of steam on its way 
from the boiler to the- cylinder ; 2. quick firing, attended 
with too small a steam room ; and both may sometimes be 
found to act in combination. To the first of these causes, 
the explosion, for instance, of one of the boilers of tho 
Parana steamer, at Southampton, a few years ago, has been 
ascribed by the Government engineer surveyor ;* to the 
second, the explosion of the copper boiler of the Comte d'Eii 
yacht, in France. According to Dr. Joule, the mere dead 
pressure of an elastic fluid is due to the impact of its 
innumerable atoms on tho sides of the confining vessel. 
When the motion of a current of steam is suddenly 
checked, as by the valve in its passage from tiie boiler 
to the cylinder, its speed and weight cause a recoil on tho 
sides of the boiler analogous to the edects of the, in this 
case, almost inelastic current of water in the hydraulic 
ram.f This action is necessarily most felt with engines in 
wiiich the steam is let on suddenly, as in the Cornish and 
other single-acting engines, working with steam valves 
suddenly affording a wide outlet, and as suddenly closing. 
It produces such phenomena as thesprin^^ing or breathing 
of cylinder covers, and the sudden oscillations of gauges, 
noticed long ago by Mr. Josiah Parkes and others.J 
Some years ago, while standing on a boiler working a 
single-acting engine, and with a deficient amount of steam- 
room, the writer noticed the boiler to slightly breathe 
with every pulsation of the engine. The same action has 
been observeil by others with boilers the steam-room of 
which is out of proportion to their heating surface. The 
intensity of the instantaneous impulses thus generated 
would be, as Mr. Parkes observes, difficult to measure, but 
their repeated action must rapidly affect the boiler at its 
mechanically weakest points. The more or less sudden 
closing of a safety-valve while the steam is blowing off 
would evidently produce the same eflfect ; and this view is 
strengthened by the fact that the great majority of loco- 
motive boilers— in which while at work there is no such 
sudden call on the reservoir of steam as in the Cornish 
engine— explode while standing with steam up at the 
8tation8.§ It is not denied that, in the case of a locomo- 
tive, the mere extra accumulation of steam from the 
safety-valves being screwed down above the working 
pressure will also come into play. But there can be little 
doubt that most boilers are subjected sooner or later^ 
and with more or less frequency, to an impulsive 
load. This being the case, this consideration alone 
would demand a factor of safety of iix in the 
designing of steam boilers. The Commissioners on 
the application of iron to railway structures, in their 
third conclusion on a mass of evidenae which has 
made their investigations the most valuable ever con- 
ducted on the strength of materials, say :— ^" That, as it 
has been shown, that to resist the effects of reiterated 
flexure, iron should scarcely be allowed to suffer a deflec- 
tion equal to one- third of its ultimate deflection, and 
since the deflection produced by a given load is increased 
by the effects of percussion, it is advisable that the 
greatest load in railway bridges, shall in no case exceed 
one-sixth of the weight which would break the beam 
when laid on at rest in the centre." || 

Emersfln showed, more than sixty years ago, that the 
stress tending to split in two an internally perfectly 

* Rudimentary Treatise on Marine Engines and Steam 
Vessels, etc. By Robert Murray, C.E., Engineer Surveyor ta 
the Hon. Board of Trade, p. 74—78. 

f Instituto di Scienze. Milano, 1829. 

X Transactions of the Institution of Civil Engineers. Vol. 3. 

§ Reports of the Inspecting Officers of the Board of Trade^ 
1850 — 64. (The four locomotive boilers which burst last year 
all did 80 while standing. Neither the primary rupture leading 
to the explosions, nor the secondary rupture caused by the ex- 
plosion, took place through the rivet holes.) 

II Report of the Commissioners appointed to* inquire into 
the Application of Iron to Railway Structures, xviii. 



cylindrical pipe, submitted to the pressure of a fluid from 
the interior, is as the diameter of the pipe and the 
fluid pressure. He also showed " that the stress arising 
from any pressure, upon any part, to split it longitudinally, 
transversely, or in any direction, is equal to the pressure 
upon a plane drawn perpendicular to the line of direc- 
tion." As in a boiler the thickness of the metal is small 
compared with the radius, the circumferential tension 
has been assumed to be uniformly distributed ; and the 
strain per unit of length upon the transverse circular 
joint being only half that upon the longitudinal joints, 
the strength of the latter has been taken as the basis 
of the calculations for the tensile strength of the 
joints. But in taking the internal diameter of the boiler 
as the point of departure, the internal section has been 
assumed to be a correct circle, which would only be 
practically true in the case of a cylinder bored out 
in a lathe, and never in that of a boiler. Two of 
Emerson's corollaries from his first proposition have in fact 
been neglected. He shows that if one of the diameters 
be greater than another, there will then be a greater 
pressure in a direction at right angles to the larger 
diameter ; the greatest pressure tending to drive out the 
narrower sides till a mathematically true circle is formed. 
The aecoiid ia that, " if an elastic compressed fluid be 
enclosed in a vessel, flexible, and capable of being dis- 
tended every way, it will form itself into a sphere."* A 
number of proofs can be adduced that both these influences 
are more or less at the bottom of the wear and tear caused 
by the direct action of the steam. 

From 1850 to 1864 forty locomotive explosions causing 
a loss of human life have occurred in the United King- 
dom. The Board of Trade reports in the Bluebooks pre- 
sented to Parliament, and more especially those by Captain 
Tyler, K.E., probably form the most valuable and con- 
nected series of records extant on boiler explosions. This 
is more especially the case with regard to wear and tear 
caused by the direct action of steam unmasked by the 
effects of the fire, as the ban-el and outside fire-box of a 
locomotive cannot be said to be under the direct action of 
the heat. Perhaps the vibration of the boiler through 
the motion on the line may intensify this action, but it 
is clear that vibration cannot be a primary cause. 
The majority of the reports are illustrated by careful 
drawings. Eighteen of the forty boilers gave way at the 
firebox — eleven frogi the crown of the inside fire-box 
being blown down upon the tube plates ; seven from the 
shells or sides giving way. Twenty burst at the barrel ; 
and two explosions may be ascribed to miscellaneous causes, 
from an originallj^ defective plate, and from running off the 
line. Leaving out all those which occurred at the fire- 
box, as the majority of these might be ascribed to other 
influences than direct pressure, all the twenty explosions 
of the baiTel could be traced either to internal furrows or 
to cracks, both running parallel with one of the longi- 
tudinal joints of one of the rings forming the barrel. All 
the joints which thus gave way were lap-joints ; and the 
furrows or the cracks (and the foimer greatly preponderate 
in number) occur at the edge of the inside over-lap, and, 
therefore, just at the point where the diminution of 
diameter caused by the lap-joint would be most affected j 
by the pressure of the steam. (See Fig. 1.) 

The plate at the channels shows distinct traces of lami- i 
nation through the cross-bending, and it is probable that 
plate of a good material will gradually laminate, while 

* The action of a fluid pressing with equal forces in all 
directions can be evidently represented as to force and direction 
by innumerable radii of equal length led from a single point 
in all directions. Upon this principle may be explained the 
spherical shapes of soap bubbles, of the bulbs of thermometers ' 
(blown while the glass was in a plastic statie), of the thin 
india rubber balls, used as playthings, and which are formed by 
forcing air into india rubber tubes closed at one end. Gas and 
air bubbles in water are necessarily flattened by the hydro- I 
static pressure. It is upon that principle that a gun of soft | 
ductile iron often bulges out at the breech. ' 

Fm. 1. 

(Full size cross section of the ftirrowed longitudinal joint in the fire 
box riag of a boiler which exploded at Overton station, on the 
30th May, 1864. It does not differ from other furrows. ) 

inferior metal will crack through in much less time. Nor 
are these furrows found with only lap-joints. Butt-joints, 
with a strip inside the boiler, and thus destroying the 
equilibrium of internal pressure, have been found to be 
attended with similar furrows. Channels of exactly the 
same character have been observed in locomotive boilers 
with lap-joints, which have exploded in Germany.* 

Similar furrows, again, have been noticed in marine 
boilers, and in old boilers generally, longitudinal far- 
rows being of course about twice as dangerous as those 
appearing transversely. The smoke-box tube-plates of 
inside cylinder-locomotive engines have been found to 
be similarly influenced by the racking action of the en- 
gines, showing furrows around the cylinder flanges. A 
parallel case' is often found in Lancashire with the end- 
plates of double-flued Fairbairn boilers, which may have 
been too stiffly stayed to the barrel. Circular furrows, 
caused by the confined motion of the end-plates are 
sometimes found at the base of the angle iron rings joint- 
ing the internal flues to the end-plates. But furrowing 
seems with no kind of boiler to be more felt than with loco- 
motive boilers. This is due to the higher pressure, to the 
thicker plates causing a coarser lap, and more especially 
to the fact that the unstayed barrel cannot be thoroughly 
examined without drawing the tubes, thereby enabling 
the fuiTOw to enlarge itself unnoticed. 

The inside fibres of a plate bent up while cold are 
necessarily initially in a state of compression. When 
the pressure from the inside comes on, striving to form a 
perfect cylinder, the plate gfets bent to and fro by its own 

• Organ fuer die Fortschritte des Eisenbahnwesens. 1864, 
p. 159. 



elasticity on one side, and by the pressure on the other. 
If the iron be brittle, it may crack right through ; if 
ductile, the outside fibres gradually lose their elasticity, 
and, necessarily aided by other causes, crack away. This 
action is progressive, and probably very rapid towards its 
later stages. Once a weak place formed itself it would 
have to do more and more of the work. Even when 
pulled by the direct tension of the testing machine, a lap- 
joint behaves in a somewhat similar way. For instance, 
a half-inch lap, solidly welded by Bertram's process, has 
only half the strength of the solid plate ;* while the 
f inch lap-weld has actually two- thirds of the strength 
of the entire plate. 

Messieurs Jean Piedboeuf and Cie., of Aix-la-Chapelle, 
Diisseldorf, and Liege, who turn out annually upwards of 
one thousand steam boilers, use a lap-joint which proba- 
bly gives slightly better results as to furrowing, while it 
s much easier to caulk, and must be therefore less in- 
ured by that process. (See Fig. 2.) 

Fig 2. 

(The edges of the plates are cut to an angle of 659, by means of 
inclined shears.) 

There is, however, another important appearance to be 
noted with respect to these furrows. An iron cylindrical 
vessel under internal pressure would of course rupture 
long before it could assume a spherical shape, from its 
ranges of elasticity and of ductility being so short. But 
it may be said to be undergoing three distinct stresses in 
as many directions. There is a stress acting on the ends, 
and tending to rupture the boiler in two halves in a direc- 
tion parallel to the axis; there is the stress which is hoop 
tension in a true circle, but w;hich acts with a cross-bend- 
ing strain in an ordinary boiler ; and there is the stress 
which tends to make it assume the shape of a barrel, or to 
bulge it out in the centre of its length. The precise action 
on a material of several strains like this is a portion 
of the strength of materials which is still completely 
unknown. ^ Its probable effects might be illustrated by 
the ease with which a stretched india-rubber ring is cut 

* ** Recent Practice on the Locomotiye Engine," p. 5, 

through with a knife, or that with which a column 
under compression is broken by a blow from a hammer, 
or by the similar ease with which a tube under tension is 
split by a sharp blow ; in fact, the operation of caulking a 
defective boiler under steam seems thus to often give it 
the finishing stroke vihich causes an explosion. The new 
boiler which burst from a defective plate at the Atlas 
Works, Manchester, in 1858, and that which burst through 
a crack at a longitudinal joint last January, at Peterbo- 
rough, both gave way whilst being caulked. This again 
accounts for the fact that adjacent boilers sometimes ex- 
plode one after the other, pointing, at the same time, to 
the danger into which a sound boiler may be thrown by 
an explosion. Upon the same principle it is probable 
that the modern guns, built up from strained rings, will 
he eaisWy put hors de combat by shot. The probability is 
that a number of simultaneous strains in different direc- 
tions diminish the elasticity of the material that would 
allow it to yield in any given direction. However this may 
be, it will be seen that it is only the pressure on the ends 
of the boiler acting parallel to the axis, and tending to 
tear the cylinder through transversely, which bears fairly 
on the rivetted joint, or rather on that metal between the 
rivets which is left after punching. Unless the cylinder 
be perfectly correct inside, the circumferential strain re- 
solves itself into croj^s-bending, shifting the dangerous 
strain from the iron left after punching to the metal at 
the over-lap. With respect to the stress tending to bulge 
the cylinder in the centre, it is clear that if we suppose a 
strip cut out from the entire length of the boiler, each 
portion of the length of this strip could be regarded as a 
beam under an uniformly distributed load. As, however, 
with the lap joint, there is a double thickness of metal 
transversely, that joint is the strongest and stitfest 
portion to resist the stresses tending to bulge out the 
cylinder in the middle, and also to tear it into two 
halves. This affords some justification for the belief 
of old boiler-makers, before rivetted joints were tried 
under a direct tensional load, that the joints are the 
strongest parts of the boiler. And, indeed, this is what 
we find in practice. The thinnest portion of the longi- 
tudinal furrows is generally exactly in the middle of the 
plate, and this is caused by the longitudinal stress, which 
is -acting at right angles to the transverse cross-bending 
stress. A strip cut from joint to joint is, in one respect, 
in the condition of a beam supported at both ends, uni- 
formly loaded throughout its length, and, according to 
known principles, therefore giving way in the middle. 
(See Fig. 3.) 

The middle ring of the boiler which burst on the 
Metropolitan Railway last year, and the fragments of 
which were examined by the writer, also first given 
way at a farrow. Captain Tyler reports that at from 
16f to 19 inches from the transverse joint, or just about 
the middle of the plate, there was " very little metal 
left holding," while it gradually got to its original thick- 
ness of f , as the groove receded from the centre of the plate 
and towards the transverse joints at each side. 

It is impossible to deny the existence of an infinite num- 
ber of stresses acting on the sides of a vessel undergoing 
fluid pressure, producing what, for want of a better term, 
might be called a ♦' bulging strain." Instances of this 
action may be noticed in the sketch of the leaden pipes 
given by Mr. Fairbaira,* which were bulged out in the 
middle by internal pressure, as also in the fire-box sidesf 
influenced by the same means, and in the centre of the 
surface. Unaccountably enough, the effect of such a 
strain on th,e ultimate resistance, and, above all, the 
elasticity, of materials, has been entirely neglected by 
investigators, and there are no published data on the 
matter. The effect of the internal pressure is evidently 
resisted by a double thickness of plate at the joints, so 

* »' Philosophical Transactions, 1858," p. 402. 
t *' Useful. information for Engineeis, 1856.** Appendix, 



Fig. 3. 

<Froin Captain Tyler's report, dated 30th June, 1864, on the boiler 
explosion at the Overton station of the London and North- Western 
Bailwaj The plate tern off is shaded, the course of fracture on 
the other side of the boiler is dotted, while the furrow is shown by 
the thick horizontal line.) 

that the load on the middle of a single ring may be 
considered as determining the weakest part of the boiler. 
One of the rings of the Great Northern boiler which 
exploded on the Metropolitan Railway last May had a 
length transversely of about (say) 36 inches from lap to 
lap, with an inside diameter of 45 inches. If we now 
suppose a strip one inch broad cut from the 36 inch long 
plate, parallel to the longitudinal axis of the boiler, this 
strip is, supposing there be a pressure of 100 lbs. to the 
square inch, uniformly loaded with 3,600 lbs. — equal to 
a transverse load of 1,800 lbs. at the centre. Supposing 
the plate to form a true circle, a hoop one inch wide of 
the I plate would be subjected, circumferentially, to a 
tensile load of 6,000 lbs. per square inch, while (leaving 
out the diminution of area at the ends through the flue 
tubes) each portion of the circle, about 1 inch broad and 
f inch thick, is subjected to a load of about 1,125 lbs. 
acting parallel to the axis of the boiler. 

To construct a general rule or formula that would take 
into account the distorting effects of the lap or of the welt 
of butt-joints would be impracticable ; but it is clear that 
the usual mode of calculating the strength of a cylin- 
drical boiler from the tensile strength of joints tested by 
weights, or hydraulic pressure, directly applied, is far from 
being correct. It is only tolerably correct with scarf welded 
joints, or with butt joints with outside welts. Even here, 
the hoop tension of the true cylinder is resolved into a 
cross bending strain, if the cylinder does not not form a 
correct circle internally. The usual fornmla would be 
practically correct, if the boiler were prevented from 
altering its shape during the impulses sometimes given by 
the steam, and the quieter buckling action caused by 
the altcinate increase and fall of the pressure. In fact 
a boiler, like a girder, does not merely demand a high 
ultimate strength, but also a stiffness which is the protec- 
tion against alternative strains — against buckling or 

Disregarding the effects of the thickness of the material, 
a perfect cylinder should theoretically afford the same 
ultimate resistance, whether exposed to extemal or internal 
pressure. Its resistance to collapse should indeed be 
greater, as most materials give more resistance to com- 
pression than to tension. This is not the case, as the 
distortion of form progressively weakens an internal 

flue, by increasing the load on its surface, whiie the 
contrary is rather the case with the boiler exposed 
to internal tension. Before Mr. Fairbaim showed the 
inherent weakness of flue tubes, their frequent explo- 
sions through collapse w^ere ascribed to spheroidal ebul- 
lition and other similar causes. They are now, according 
to the engineer of the Manchester Boiler Association, 
stronger than the shells, by means of the J- iron and angle- 
iron bands now generally used, and also by the excellent 
seams introduced by Mr. Adamson so long ago as 1852.* 
While J-iron and other bands could be used for the 
barrels of boilers not exposed to the fire (as is recom- 
mended in Francef and by the Board of Trade Inspector 
of Bailways), Adanison's seams reversed would probably 
form excellent transverse joints for a shell fired from the 
outside, and, with a boiler like this, thin and narrow plates 
could be used, affording a stronger and tighter lap-joint. 
With a construction of this kind little or no deflection or 
bulging cculd occur, and the sectional area of the plate 
and the rings would really give the strength of the boiler. 

2. — The Mechanical Effects of the Heat. 
While a maximum of stiflness to the mechanical 
action of the pressure is required in a steam boiler, 
a maximum of flexibility to the irresistible mechanical 
force of heat is of no less importance. For instance, a 
great advantage of some of the forms of strengthening 
rings for internal flues is that they allow the use of 
thinner plates ; together forming a structure of great 
flexibility to complicated thermal influences. The 
longitudinal expansion of inside flues like this is taken up 
by a slight spring or swagging at each joint, and the end 
plates of the shell are not unduly strained by the combined 
efilorts of the iiiternal pressure and the expansion due to 
heat. This is one way in which defective circulation, or 
a sudden current of cold air or of water, can act on the 
structure, by unequally straining the plates ; and, although 
it seems probable that the effects said to have been thus 
produced, are, to some extent, due to other causes, they 
point to the importance of keeping the temperature of 
the plates as low as possible. One protection against 
effects of this kind is the gradual diffusion of heat, pro- 
duced by its conduction to and from the different plates. 
It is a general belief with engineers that a pressure of 
steam strains a boiler more than cold hydraulic pressure f 
but it is unsettled as to what amount and in what exact way. 
The basis of an examination of the kind would have to be 
sought in an exact determination of the temperature of a 
plate which is transmitting the heat to the water, and this 
has not yet been determined with any accuracy. The 
fact is, as is remarked by M. Pcclet, who has given 
great attention to these questions, the.different phenomena 
involved are extremely complicated. It is clear that the 
plates must always be at a higher temperatdre than the 
water, as it is by the difference of temperature of the two 
surfaces of the plate that it is traversed by the heat. He 
supposes that, though the flow of heat through the plate 
is inversely as its thickness (while it is directly as the 
surface and as the difference of temperature between the 
outside and inside faces), yet the flow of heat would be the 
same through a thicker plate, from the greater difference 
of temperature between the two surfaces.}: He does not 
seem, however, to be aware of the important law demon- 
strated by Mr. J. D. Forbes, that the conducting power of, 
for instance, wrought iron, rapidly diminishes at the higher 
temperatures. At 200° C. it has little more than one- half 
the conducting power it has at 0^.§ At yet higher tem- 
peratures it might probably be proved , if an applicable instru- 

* Specification No. 14.259. 

t Bulletin de la Societe' Industrielle de Mdhouse, 1861, 
p. 632. 

t Traits de la Chaleur. Vol. 2, p. 393. 

g Royal Society of Edinburgh, 28th April, 1862. '* Ex- 
perimental Inquiry into the Laws of the Conduction of Heat 
in Bars, and into the. Conducting Power of Wrought Iron." 



ment for registering higher temperatures were in existence, 
that the powers of conduction are still less. Some of Mr. 
Peclet's experiments also seem to be vitiated by his disregard 
of Dr. Joule's discovery that water is heated by being me- 
chanically stirred up. It is, however, certain that water can 
only moisten a metallic plate when at a lower temperature 
than 171° C. As soon as the water gets thus repelled, 
the heat radiated by the metal is reflected back from the 
surface of the liquid ; the metal gets hotter and hotter, 
with a corresponding diminution of its conducting powers ; 
its outside, exposed to the fire, would more or less oxidise, 
and with a similar result ; and a like effect is produced 
on the inside — on the roughened surface of which incrusta- 
tion would rapidly adhere, forming a calcareous coating, con- 
ducting with about sixteen times less power than iron.* 
All these tendencies are of a progressive character, lead- 
ing to very high temperatures in the plate, even to a red- 
heat. This tends to explain how rivet-heads close to the 
fire are soon burnt away by the friction of the current of 
heated gases on the red-hot metal ; how thick fire-boxes 
are sooner burnt out than lighter ones, the process being 
often arrested at a certain thickness ; how internal flues 
of thick plates so often give trouble; how externally 
fired boilers are most deteriorated at the corners from 
the junction of the three plates ; and similar results well 
known to practical men. Another proof that thin plates 
conduct more heat than thick plates is afforded by some 
experiments lately made in Prussia, with two egg-end 
boilers, exactly similar in every respect, except that one 
was constructed of steel plate J inch, while the other was 
of wrought-iron about J inch thick. The steam gene- 
rating power of the steel boiler was to that of iron as 
127*49 to lOOf — a result which can only be accounted for 
by the relative thickness of the plates. Thick plates are 
also more liable to blisters, one of which would con- 
siderably diminish the conducting power of the spot where 
it happened to form. 

While it is certain that boiler plates can assume very 
high temperatures, even up to red-heat, authorities 
differ as to the diminution of ultimate strength which is 
caused by heat, while its effect on the elasticity of the 
plate has been scarcely attended to. The experiments on 
the ultimate tenacity of iron at high temperatures, con- 
ducted by Baudrimont, J Seguin, and the Franklin Insti- 
tute, can scarcely be looked upon as of much value, for 
they were made on a very small scale, and with no re- 
gard to the temporary and permanent elongations — or to 
the effect of heat on the elasticity and ductility. 

Mr. Fairbairn§ observed no effect on the strength of 
plate iron up to almost 400° F. At a " scarcely red " heat 
the breaking weight of plates was reduced to 16-978 tons 
from 21 tona at 60° f. ; while at a '* dull red " it was only 
13-621 tons. MM.Tiemery andP.SaintBrice,|| aided by 
thecelebrate'd Cagniard Latour, found that at nominally the 
same temperature [rouge sombre)^ a bar of iron was reduced 
in strength to one sixth of its strength when cold. This 
is much greater diminution of strength than that found 
by Mr. Fairbairn. Apart from other causes, this might 
easily be due to the fact that incandescent iron affords a 
different tinge during a dull day to what it does in a clear 
light. In fact, the great impediment to all these in- 
vestigations is the want of a thermometer for high 
temperatures; but M. Tr^m^ry's result is perhaps more 
conformable with daily experience. Mr. Fairbairn's data 
would show that the ultimate strength of wrought iron is 
reduced to about one-half ; but M. Tremery's result ex- 
plains the generally instantaneous collapse of flues when 

* Traits de la Chaleur. Vol. i., p. 391. 

t Verhandlungeu des Vereins zur Beforderung des Gewerb- 
fleisses in Preussen, 1862, p. 140. 

X *'AnnaIes de Chimie et de Physique," 3, s. 30, p. 304, 

gOn the Tensile Strength of Wrought Iron at Various 
Temperatures. Eeports British Association, 1856, p. 405. 

II Annales des Mines. 2 serie. Vol. iii., p. 513. 

red-hot, and which have been of course originally cal- 
culated to a factor of safety of six. 

A most important question is the effect of temperatures, 
whether high or low, on the elasticity of the material — 
whether iron will take a permanent set with greater 
facility at a high temperature ? These data are really 
more important than those on the ultimate strength, as 
they would show the influence of temperature on the 
elastic limit. Here again is a vacancy in existing know- 
ledge, which can scarcely be said to be filled up by the 
few experiments of the late M. Wertheim on very small 
wires.* He found, however, that the elasticity of small 
steel and iron wire " increases from 15*^ C to 100"^, but at 
200° it is not merely less than at 100°, but sometimes 
even less than at the ordinary temperature." 

There is, however, another very important point with 
respect to wrought iron, which has scarcely received the 
attention it deserves. As would appear from a number 
of phenomena, there seems to be a sort of thermal elastic 
limit with iron. When heated, and when its consequent 
dilatation of volume does not exceed that which cor- 
responds to (perhaps) boiling point, it returns to it& 
original dimensions. Beyond a certain temperature it 
does not contract again to its pristine volume, but takes a 
permanent dilatation in consequence, apparently, of its 
elastic limits having been exceeded. A number of observersf 
have determined the fact with calt iron, and though 
wrought iron has not been expressly investigated in thia 
direction, there is no doubt that it exhibits a similar 
behaviour. Thus, a number of years ago,J an Austrian 
engineer, named C. Kohn, remarked that a boiler about 
12 metres long and 1-57 in diameter, with a thickness 
of plate of 0.011, permanently expanded, at a tempera- 
ture corresponding to a steam pressure of 5 atmospheres, 
(153° C.) by 0.07193, and did not, when cold, return to 
its original dimensions. The same thing has been noticed, 
by means of very accurate measurements, with other boilers* 
A number of experiments by Lt.-Col. H. Clerk, of Wool- 
wich, on wrought iron cylinders and plates,§ bear distinct 
evidence to a dilatation of volume in wrought iron, when 
repeatedly heated and suddenly cooled. In experiment 
7, for instance, " two flat pieces of wrought iron, each 12 
inches long, 6 inches deep, and J inch thick, were heated 
and cooled twenty times, one being immersed to half, and 
the other to two-thirds, its depth in water. That im- 
mersed one half contracted or became indented on the 
ends fully -3 inch ; the other had similar indentations, 
but only to one-half the amount. They both turned up 
into the foim of an arc," the convex side of which 
appeared in the portion heated and cooled. Unfortunately, 
the specific gravities of the different portions were not 
tried by Colonel Clerk. A succession of trials of 
the kind produced cracks in the metal, thus explain- 
ing how boiler plates are cracked by imperfect circulation 
and by cold feed-water let in near the fire ; and, 
the thicker the plate, the more permanent dilatation of 
volume and consequent danger. Mr. Kirkaldy found 
that " iron highly heated and suddenly cooled in water, 
is hardened," being injured, in fact, if not afterwards 
hammered or rolled. This permanent dilatation of volume 
nmst be necessarily accompanied with a diminution of 
specific gravity, thus affording another close analogy 
between straining iron by loads in excess of the me- 
chanical elastic limits, and straining by heat. Lajerhelm|| 
found long ago that the specific gravity of iron is di- 
minished by stiains in excess of the limit of elasticity, 
and this result has been completely confirmed by Mr. 
Kirkaldy's numerous experiments. The smith calls iron 
'* burnt" which has been rendered brittle in working 
through the often repeated applications of heat, or through 

* GoDiptes Reodus, xix.,231. 

t Percy's Metallurgy, vol. ii., p. 872. 

X Tecbnologiste. 1850-51, p. 102. 

i Proceedings of the Royal Society, March 5, 1863. 

11 Poggendort's Annalen, 2 s., vol. ii>, p. 488. 



too high a temperature. Iron rendered brittle by strains 
in excess of the limit of elasticity has been long popu- 
larly termed " crystallized." Both these states are ac- 
companied with a dilatation of volume and attendant 
hardness and brittleness, and both seem to be referable to 
very similar causes. In fact, a very general belief exists 
that very ductile good iron, used in the form of a steam 
boiler, soon gets brittle. There are some. applications of 
metal to a steam boiler peculiarly liable to be strained 
beyond the limits of elasticity ; by mechanical force, by 
the mechanical force of expansion and contraction, and by 
dilatation of volume through heat all three acting simul- 
taneously. Such is the case with fire-box stay-bolts. Ac- 
cordingly, they are found to get very brittle when of 
wrought iron — which is a much less ductile metal than 
copper. Mr. Z. Colburn states that he has "frequently 
found these stays (where made of wrought iron) to be as 
brittle, after a few years' use, as coarse cast iron." He 
has " broken them off from the sides of old fire-boxes, 
sometimes with a blow no harder than would be required 
to break a peach- stone."* 

3. — The Chemical Effects of the Incandescent 

Whatever physical changes may be induced in iron by 
• the long continuance of a high temperature which is not 
succeeded by the application of the impact of the hammer 
or the pressure of the rolls, it is certain that long-con- 
tinued red heat leads to the loss of its metallic consistency. 
Its surface gets converted to a greater or less depth into 
forge scales, which, according to Berthier, consist of a 
crystallized compound of peroxide and protoxide of 
iron. The mechanical action of the gases — and especially 
of the free oxygen contained in every flame — forced at a 
high velocity by the draught past the more or less heated 
plates, would also aid these chemical combinations — upon 
the same principle as iron '.filings, thrown through a gas 
flame, burn in the air ; and upon the same mechanical 
principle as the incandescent lime is worn away by the 
flame of the oxy hydrogen blow-pipe. These actions would 
take place with any fuel, even with pure charcoal. But 
when mineral fuel, which mostly contains more or less iron 
pyrites, is used, there is much more danger to the 
plates, especially over the fire, in getting red hot, as the 
flames would then hold sulphurous acid, and often 
volatilised sulphur. A familiar illustration of an action 
of this kind is afforded by the fact that a piece of red- 
hot iron plate can be easily bored through by means 
of a stick of sulphur, the combination forming sulphide 
of iron. Dr. Schafhaeutl, of Munich, has given great 
attention to the changes in plates subjected to the 
action of fire ; twenty-five years ago he read a paper 
before the Institution of Civil Engineers,! and more 
recently h(; has published an essay, both on this sub- 
ject, in a Munich periodical.J He has brought forward a 
number of facts, founded on chemical analyses of plates of 
exploded boilers, showing the danger, due to chemical 
action alone, when the plates of a boiler become red hot. 
He notices that the iron of the inside of the plates, in getting 
red-hot, decomposes the water, and combines with theoxy- 
gen thus freed. It also loses some of its carbon. The out- 
side combines with the free oxygen and with any sulphurous 
acid in the flame. He states that iron made with pit 
coal is much more affected than charcoal-made iron ; 
becoming laminated at the original joints in the pile out 
of which the plate has been rolled. It is possible that 
portions of oxide are carried into these joints, and it is at 
any rate certain that iron gives way easiest at these 
places. This points to the great value of really homo- 
geneous plates, such as those of cast steel, in which homo- 
geneityhas been obtained bythe only known means of fusion. 

* Steam Boiler Explosions, 1860, p. 32] 
t Transactions of the iDStitation of Civil Engineers. Vol. 
iii. 1840 ; p. 435. 
t Bairisches Kunst und Gewerbeblatt. June, 1863. 

The remarkable diminution of elasticity and of tenacity 
caused by the combination of the red hot iron with sulphur; 
the absence of all elasticity and tenacity in the oxides of 
iron, show that, even if a flue do not at once collapse, or 
a shell explode, through getting red-hot, the boiler is 
more or less injured every time it gets overheated. A 
defective circulation, by permitting such a temperature 
as to drive the water off the plate, would soon lead to 
local injury. Particular spots in externally fired cylin- 
drical boilers are sometimes, as is stated by Mr. L. Fletcher 
of Manchester, thus affected, and in an apparently 
mysterious way. A new boiler in which a heap of rags 
were accidentally forgotten, had the spot burnt out in a 
few days,* doubtless through the resulting defective 
circulation and its consequences. The plates just above 
the fire of internal flues also suffer in this manner. It is 
perhaps possible that turned joints, secured by bolts, and 
allowing an occasional reversing, or rather rotating, of the 
ring, might, in some cases, be here of service. At any 
rate, universal experience proves that the thicker the plate 
the easier does it get red hot; and these chemical facts also 
point to the desirability of a minimum of thickness. In 
fact, the wearing away of the plates through these causes, 
if mechanically strong against pressure, often gets arrested 
at a certain thickness. In Germany and France, some of 
the best manufacturers still make the plates over tiie &m 
of, for instance, inside flues, slightly thicker than anywhere 
else ; but the combined chemical and mechanical actions 
of the heated fuel cause most wear and tear in a thick 
plate, and thus justify American practice in this respect. 
In that country, fire-box plates of good charcoal iron are 
made only -^-^ or J of an inch thick, and, with stays four 
inches apart, give good results under nearly 150 lbs. steam 

4. The Chemical and Physico-Chemical Effects op 


The wear and tear of a boiler which occurs in the form 
of corrosion, properly so-called, may be divided into two 
principal kinds:— (1.) Internal, and (2.) external. The 
progress of both is necessarily intensified by the mere 
effects of temperature ; each, however, has its strongly- 
marked, distinct character— not merely as to position, but 
also as to origin and results. 

A steam boiler is in the position of a vessel into which 
large volumes of water are continually forced ; while the 
heat applied, driving oft" all volatilizable matter, leaves be- 
hind a concentrated solution with a chemical character de- 
pendent on that of unvolatizable matters in the feed- water. 
The specific gravity of the substances found in the water 
naturally causes them to sink towards the bottom, at 
which part the solution is generally more concentrated, 
however much it may be stirred up by the ebullition*. 
Mr. J. R. Napier lately stated that a piece of zinc " about 
four feet long, by three inches broad, by three- sixteenths- 
thick, placed in a marine boiler for three weeks " to a 
f'.epth of 18 inches in the water, showed a corrosion 
which rapidly decreased " up to the highest part, 
which, in the steam, appeared to be little aff'ected."f 
This accounts for the fact that all boilers, even those in- 
ternally fired, like locomotive boilers, have their plates 
most affected towards the bottom, end that internal 
corrosion always shows itself to a greater extent below the 
water line. The houilleur of the form of boiler knowa 
as the French boiler is also generally more affected than 
any other part. To resist this sort of slow action, it is 
clear that the more the bulk of metal the better, and it 
is for this reason that the bottom plates of most marine 
boilers are made thicker, while these same plates in locomo- 
tive boilers have to be often renewed. Any chemical or 
physico-chemical action of the kind is of course intensified 
by temperature, and this is one of the causes why ex- 
ternally fired boilers give way most a little in front of 

* Peclet, Traits de la Chaleur. Vol. ii., p. 73. 

t Institution of Engineers in Scotland, Session 1864—5. 



the furnace. But the plates above the water-line also 
get more or less coiToded, and not merely with the usual 
character of rusting, but in that peculiar form known as 
pitting, which generally shows itself much more strongly 
marked below the water-line. 

The presence of a concentrated solution of an acid or 
alkaline character, kept at a high temperature for years in 
contact with iron plates, would be sufficient to account 
for much corrosion. But the internal corrosion of steam 
boilers has many features of such a mysterious character, 
that no accredited explanation of its attendant phenomena 
has yet been put forward. In the first place, plates thus 
attacked show a number of irregular holes like a pock- 
marked human face, or like the small craters seen on 
the moon*8 surface. (See Fig. 4.) The writer has 

Fig. 4. 

{The internal surface of a plate of an old wrought iron boiler, showing^ 
one-quarter of the full size, the ordinary appearance of pitting.) 

also sometimes observed two or three little irregular 
excavations like this in a plate otherwise showing a large 
surface quite intact. Sometimes the plate is most pitted 
round a projecting bolt ; at others, one plate will be per- 
fectly sound, while thatrivetted to it will be almost eaten 
away, both having been the same time at work, and 
under, of course, apparently exactly similar conditions. 
With locomotive boilers this pitting has been ascribed to 
galvanic action between the brass tubes and the iron 
plates. But it is notoriously well-known to locomotive 
euperintendents, that boilers with iron tubes are often 
worse pitted than those which have run the same distance 
with brass tubes. Besides, all iron boilers, with or with- 
out brass, whether used for stationary, locomotive, or 
marine, purposes, ape subject to pitting. 

An explanation which seems to meet all the circum- 
stances of the case is the following : — Mr. Mallet, in a 
report addressed to the British Association some years ago, 
showed that wrought iron and steel (blister steel probably), 
" consist of two or more different chemical compounds, 
coherent and interlaced, of which one is electro negative 
to the other." In fact ordinary wrought iron, being also 
welded up from differently worked scrap, is far from being 
an electro- homogeneous body. In a boiler, the hot water, 
more or less saturated with chemical compounds, is the ex- 
citing liquid, and the electro-positive portions of the plates 
are thus quickly removed to a greater or less depth. 
This explanation meets most of the known circumstances 
with respect to pitting ; it even, in a great measure, ex- 

plains how plates above the level of the water, especially 
in marine boilers, get very rapidly corroded in portions, 
while another part of perhaps the same plate is scarcely 
affected. The concentrated water in a marine boiler is 
known tp be generally acid. *• Of all the salts contained in 
sea -water, " says Faraday,* " the chloride of magnesium is 
that which acts most powerfully" on the plates. He shows 
that a cubic foot of sea- water contains 3*28 oz. of this salt ; 
and, at the same time, points to the danger of voltaic action 
in a boiler through the contact of copper and iron. In a 
smaller degree the contact of cast witli wrought iron, or 
between the different makes of wrought iron in the same 
plate, or between contiguous plates, acts in the same way. 
It is not improbable that some hydrochloric acid is present 
in the steam of marine boilers. ** Mr. J. C. Forsterf has 
tested some of the condensed steam from the safety-valve 
casing, and from the cylinder-jacket of the Lancefield, 
and I'ound both decidedly acid."| With an exciting liquid 
in the condensed steam, it is thus explicable how the 
plates of marine boilers often get corroded in a most 
capricious manner; while, at the same time, the current 
of steam would create a certain amonnt of friction on the 
oxide, clearing it away to act on a fresh surface. 

The crucial test of this explanation of pitting would 
be the observation of the absence of the phenomenon 
from plates of an electro-homogeneous character. This 
homogeneity could only be expected from fused metal, 
such as cast-steel. Accordingly, while the writer was 
in Vienna a short time ago, he was assured by Mr. 
Haswell, the manager of the Staatsbahn Locomotive 
Works, that some locomotives made of cast steel plates 
in 1859, for the Austrian Staatsbahn, had been working ever 
since without showing signs of pitting, though under similar 
conditions iron plates had severely suffered in this way. 
Pitting may thus be fairly defined as a form of corrosion 
localised to particular spots by voltaic action. It is also 
probably aggravated through the motion of the plate by 
mechanical action, and the expansions and contractions 
through alternations of temperature. All boilers are 
most pitted nej^r the. inlet for the feed water, and with 
inside cylinder locomotive boilers there is generally 
more pitting at the smoke-box end — no doubt caused by 
the more or less racking action on these plates. A state 
of corrosion at particular spots would probably be kept 
up to a greater intensity by the incrustation being me- 
chanically thrown off. With a quicker voltaic action, 
caused by any unusual intensity, of the exciting liquid, 
the sides of the cavities in the plates would be sharper 
and less rounded off'; as in the case of the boiler fed with 
mineral water from ironstone workings, which exploded 
last year at Aberaman, South Wales. (See Fig. 5.) 

The fact that pitting occurs in marine boilers when dis* 
tilled water from surface condensers is used, does not affect 
this explanation. Water distilled in this way, from what- 
ever cause, after repeated boiling, is stated to carry the sali- 
nometer even higher than sea water, thus proving that it is 
not pure.§ In the next, there is the absence of incrustation, 
which to some extent always protects the plates of boilers 
from the chemical action of its contents. In this way the 
mechanical buckling of the plates, — directly and indirectly 
causing the furrows we have spoken of — by continually 
clearing particular lines of surface from incrustation and 
oxide, reduces these particular spots, with respect to corro- 
sion, to the condition of the plates of a boiler fed with 
water which deposits no incrustation. Corrosion will also 

* Fifth Report of the Committee of the House of Commons 
concerning the Holyhead Roads, p. 194. 

t Institution of Engineers in Scotland, 1864—5. Intro* 
ductory address by Mr. J. R. Napier. 

t When a solution of chloride of magnesium is evaporated 
nearly to dryness, the salt and the water are decomposed, mag. 
neda and tree bydrochloric acid Jbeing formed ; or M g C 1 + 
HO = MgO + HCl. 

§ Institution of Mechanical En«;ineers, 3863. Discussion 
on Mr. James Jack's paper *' On the Effects of Surface Con- 
densers on Steam Boilers.*' 



Fia. 5. 

(From a photograpli of surface of corroded plate cut from one of 
the two boilers that exploded on Wednesday, February 17th, 18G4, at 
Aheraman Iron Works, Aberdare. The corrosion was internal, and 
in some parts the plate was not more than one- eighth thick. Thirteen 
persons were killed, and many others seriously injured.) 

act more rapidly at a farrow through mere increase and 
renewal of surface. To resist that form of internal cor- 
rosion specially known under the name of pitting, a 
maximum of electro- homogeneity is evidently required in 
all the component parts of the boiler. 

While the action of internal corrosion, often very 
equally corrugating the plates over a large surface, as a 
rule scarcely, at any rate only gradually, affects their me- 
chanical strength, external corrosion, being localised to 
particular spots, is of a much more dangerous character. 
The one is gradual and easily perceptible, while the 
Other is rapid and insidious in its progress. Apart from 
accidental circumstances affecting the brickwork on 
which a stationary boiler is erected, or the outside of 
the bottoms of marine boilers, it is clear that 
external corrosion can only occur through leakage. 
When leakage takes place through a crack in the plate 
caused by mechanical action, or at a hole burnt out 
by heat, the effects of leakage are only secondary results, 
due to a primary cause which of itself may cause the stop- 
page of the steam generator. But a leakage at a joint may 
in itself gradually cause the destruction of the boiler. 
Here we see another reason that the character of a boiler, 
not merely as to ultimate strength, but also as to wear 
and tear, intimately depends upon the form of its 
joints. It is often noticeable that very good lap joints, 
even when tested under hydraulic pressure up to only 50 
per cent, above the werking load, sweat more or les«i. The 
tendency of the internal pressure to form a correct circle 
bears indirectly on these joints, causing them to open, 
more or less, and to leak, in spite of the caulking. Mr. 
Robert Galloway, C.E., who, as an Engineer Surveyor of 
long standing of the Board of Trade, has probably made 
more than three thousand careful inspections of marine 
boilers, states that he has often noticed a furrow or 
channel on the outside of the joint, running parallel to 
the outside overlap for some distance, and evidently 
caused by leakage. Along the water line, condensed 
water will act on the joints, while below it the concen- 
trated contents of the boiler will come into chemical action 

A leakage in a marine boiler often eats away a plate 
within a year. In some cases a jet of hot water from a 
leakage has a frictional action ; in fact, even with such an 
incorrodible and hard substance as glass an effect like this 
has been perceived, and a slight leakage continued during 
several days sometimes produces a noticeable furrow on a 
glass-gauge tube. With sulphurous fuel, a powerful 
chemical-action will come into play on the plates. One 
volume of water takes up about thirty volumes of sul- 
phurous acid gas ; and these sulphurous fumes of the fueU 
coming into contact with the water from a leakage, will 
be more or less absorbed. An acid solution like tiiis 
must quickly eat away the plate. It is certain that a 
leakage acts much quicker on a boiler fired with sulplnuous 
fuel than on one fired with wood. M. G. Adolphe 
Hirn has observed a plate, nearly seven-eightlis thick, to 
be pierced, in the course of time, as with a drill, by means 
of a little jet which struck it after passing through a 
current of hot coal smoke.* 

LiEGiSLATivE Enactments. 

No stronger proof can be adduced of the empirical state 
of existing knowledge of the management of boilers than 
that afforded by a consideration of their average duration. 
While some marine boilers last only about three years, 
there are carefully worked land boileis which have lasted 
as long as thirty. Captain Tyler, U.E., estimates the 
average duration of a locomotive boiler at from five to 
twent}' years. Perhaps the average duiation of a marine 
boiler may be reckoned at from five to seven years ; that 
of a locomotive boiler at from eight to nine years ; that of 
a stationary boiler at from eighteen to twenty years — all 
being supposed to be fairly worked under ordinary con- 

It is clear that, subjected as a steam boiler is to so many 
destructive influences, the precise effects of which can 
scarcely be yet very accurately known, the working tension 
should be only one-eighth of the ultimate bursting 
strength. But when boilers, as is too often the case in 
England, are bought by the weight ; when cheaply 
paid labour is employed in their management; when 
inspection of the progress of the wear and tear neces- 
sarily happening even with good boilers and good attend- 
ance, is procrastinated for the sake of gain, there is 
then a suit of expense versus risk, in which parsimony 
too often gains the day. At any rate, a number of 
painful accidents in all parts of the world have, at 
different times, pointed to the fact, that every man 
picked at hap-hazard cannot be safely trusted with 
steam-power. In fact, there is probably no civilised 
country in which the legislature has not more of 
less interfered in the management of steam boilers. In 
the States of America, the frequency of boiler explo- 
sions has in some localities produced a more despotic 
interference than perhaps anywhere else. In the 
city of New York, boilers are under the supervision or 
the municipal police ; they are tested periodically ; and, 
as a result, many are condemned every year. By an 
enactment of Congress, applicable to all the States,f 
steam passenger vessels are subjected to Government in- 
spection. The 13th section of this Act shows a very 
acute perception of the real cause of a boiler explosion, 
" which," it states, " shall be taken as full primA facie 
evidence " of negligence on the part of the owner, upon 
whom is thus put the onus of disproof. The law of 
LouisianaJ is particularly severe, requiring the application 
of a hydraulic test threefold that of the working pressure* 
Of course, there is a great distinction between enacting a 
law and putting it into practical execution, and it is 
probable that laws like these could only be carried out 
by organised bodies of police, like those on the continent. 
In France, in 1810, 1825, 1828, 1829, 1830, 1843, and 

* Bulletin de la Society Industrielle de Mulhouse, 1861, p. 
t Session of Congress, July 7, 1838. 
X Baltimore American, 1835. 



lastly on the 25th of January, 1865, as many different 
regulations have been issued with respect to steam 
boilers of all kinds. Beginning by requiring that every 
boiler, even of wrought iron, should be submitted to a 
hydraulic test of five times the working pressure, this 
has been successively lowered down to a threefold pressure 
in 1843, and lastly to a twofold pressure, by the Imperial 
decree of this year.* The previous law fixed the mini- 
mum thickness of the plates — a regulation which 
undoubtedly did much injury to boiler making in France. 
The old Prussian regulation of the 6th of May, 1838, 
also fixed the thicknesses of the plates, but did not 
require any hydraulic test. By the Regulativ\ of the 
31st of August, 1861, this was completely altered. The con- 
struction of the boiler was left entirely in the hands of the 
maker ; but stationary boilers had to withstand a three- 
fold, and locomotive boilers a twofold, hydraulic pressure. 
In the same way as with the present French law, the 
test had to be repeated after any considerable repairs. On 
the 5th of March, 1863, a ministerial decree reduced the 
testing pressure for old locomotive boilers down to 1 J of 
the working pressure ; and another Circular Erlass, pub- 
lished on the 1st of December,' 1864, reduced the test for 
all kinds of boilers down to twice the working load. 
There is now no material difference between the French 
and the Prussian regulations respecting boilers; and it 
may be expected that those continental states, such as 
liussia, Switzerland, and Spain, which have more or less 
copied the old French law of 1843, will also adopt the 
present alterations. There is also some talk about 
altering the present Austrian law,J which determines the 
thickness of the plates, but only demands a double pressure 
test. The Belgian rSglement % also requires double the 
working pressure for common boilers, but only IJ for 
tubular boilers. According to Article 31, the test must 
be annually applied to locomotive, portable, and marine 
boilers, as also after all considerable repairs. There does 
not seem to be any general law in Italy, but in the special 
acts authorizing railway companies, similar requirements 
to the French regulations are laid down, and govern- 
ment commissioners see that they are carried out. Each 
of the smaller German states also has its law, more or less 
like that of France and Prussia. Mecklenburg- Strelitz|| 
requires that common boilers be proved to three, and 
tubular boilers to twice the working pressure ; to be re- 
newed every fourth year, and every time that the 
boiler is repaired or altered ; Saxony,^ that cylindrical 
boilers be tried to twice the working pressure, and tubular 
boilers to a pressure three atmospheres above it. Bavaria** 
now requires double the working power pressure for new, 
and one and a half for old boilers ; while both Hanover 
and Brunswick each have a somewhat similar regulation.ff 
The French law, and indeed most of the others, require 
two safety valves ; and many are extremely minute in 
their directions with respect to glass gauges, steam gauges, 
and other fittings. In Great Britain there are no express 
legislative enactments with respect to boilers beyond those 
stated in two clauses of theMerchant Shipping Act, }J 
according to which (1) one safety-valve in every boiler of 
a vessel carrying passengers shall be placed beyond the 

*Decret concernant la Fabrication et lEtablissement des 
Machines k Vapeur. 25 Janvier, 1865. 

t DiisselJorfer Zeitung. 24 ste September, 1861. 

t Ileichs- Gesetz-Blatt fuer das Kaiserthum Oesterreich, 1854 ; 
p. 229. 

2 Minist^re des Travaux Publics, Machines h Vapeur. — 
R^gleraent. Donn^ a Laeken le 21 Avril, 1864. 

II Grossherzoglich Mecklenburg -Strelitzer Offizieller An- 
zeiger, No. 11, 1863. 

GesetzlicheVerordnungen, die Anlefiung von Dampkesseln 
betreffend. Dresden, Meinhold und Soehne, 1865. 

**Regierungs-Blattfuer das KcBuigreich Bayern, 22 Pebruar, 

tt Gesetz-Sammlung fuer das Koenigreich Hannover, ]863. 

HX Merchant Shipping Act, 27th June, 1854, Nos. 289 
and 298. 

control of the engine-driver; and (2) any overloading of this 
valve is made punishable by a fine of not more than £100, 
'* in addition to- any other liabilities" which may be in- 
curred by such an^act. The boilers of all vessels carry- 
ing passengers, befbre clearing out of port, are subjected 
to a careful inspection by an engineer-surveyor of the 
Board of Trade, who' can require the boiler to be tested 
in the usual way to twice the working pressure ; and, if 
he think fit, he can, as the result of such an examina- 
tion, place the option before the shipowner of either 
lowering the working pressure or renewing the boiler. 
Armed with such powers, the government surveyor is 
also responsible for any explosion which may directly 
occur through wear and tear. When an explosion takes 
place on a passenger railway, one of the Board of Trade 
inspectors of railways examines the fragments and re- 
ports upon the accident to the government board, w^ho 
communicate it to the lailway board. The reports are 
then printed, in order to be presented to Parliament, 
and this is the extent to which the British government 
can interfere in these cases. As with other railway acci- 
dents, however, the Board of Trade inspector is examined 
as a witness in any action for damages against the rail- 
way company. All other boilers in the United Kingdom 
are worked without any government or municipal inter- 
ference whatsoever. Within late years, however, private 
companies (the first of which was organised by Mr. Fair- 
bairn, of Manchester) have been formed for the prevention 
of boiler explosions. In return for a small annual fee, or 
for a small annual insurance premium, the boilers of any 
subscriber or insurer are periodically inspected, and, if re- 
quired, tested by skilled engineers. There can be no 
doubt that these companies have already prevented a 
great amount of loss and disaster. 

It may thus be said that there are three distinct plans for 
the general management of steam boilers: — 1. There is 
the continental plan ; 2. the free English and American 
mode ; 3. what may be termed the Manchester system. 
The continental mode consists in a strict supervision, 
sometimes ruled by formulae, of the original construction, 
and there its action may be said, for the most part, to end. 
It does not, and cannot, without periodical inspections, take 
into account the effects of wear and tear. It may even 
be doubted whether the old French law, for instance, did 
not do more harm than good as regards construction. 
The official formula, according to which were calculated 
the thicknesses of the plates, founded as it was upon the 
assumptions that a cylindrical boiler formed an exact 
circle, and that a plate, however thick, conducted the 
same amount of heat to the water, was obviously incorrect. 
What may be termed the ordinary English and American 
plan throws the onus of proof of the negligence of the 
owner on those damaged by an explosion. This system is 
subject, besides other difficulties, to all the objections that 
exist against the trial of scientific questions by a jury, not 
composed of experts, and unaided by scientific witnesses. 
The continual occurrence of explosions in those cities and 
States of America in which boilers are used without any 
supervision by the authorities, and their undue occurrence 
in England with boilers that are not subjected to syste- 
matic inspection, sufficiently prove that steam boilers 
cannot be worked at hap-hazard. On the other hand, the 
system of organised inspection by the English boiler 
companies, and the similar system according to which the 
passenger vessels are inspected by government officers, 
have given universal satisfaction. A proper estimate of 
the value of the Manchester and Board of Trade system, 
compared with the continental and with the laisser 
/aire plans could only be well based on numerous 
statistics. Unfortunately, such do not appear to have been 
formed. It is stated,* however, that in a average 
of 277 boilers, there were two explosions in the ITrench 
department of the Haut-Rhin within ten years; and, 

* Bulletin de la Societe Industrielle de Mulhouse, 1861, 
p. 525. 



from 1856 to 1861, or within five years, there were only 
two explosions in an average of 1371 boilers, under the 
care of the Manchester Association. About four explo- 
sions occur annually amongst the 6,500 locomotives 
of the United Kingdom; tliree have ah-eady taken 
place this year. In an average of 600 passenger 
vessels inspected under the Steam Shipping Acts, only 
three explosions occurred since 1846-7 in Great Britain; 
viz : one at LowestofF, in the Tonning ; another at 
Southampton, in the Parana; and a third at Dublin. 
These last results speak very highly for the care and 
abilities of the Engineer Surveyors of the Marine De- 
partment ; and the continental system is thus clearly 
inferior to that adopted by the Board of Trade. What 
is evidently wanted is that the system of skilled 
periodical inspection should spread over tlie kingdom. 
To a certain extent this is taking place, but this progress 
is slow, and needs some stimulus, while it is doubtful 
whether, in out of the way districts, the mere expense 
of inspection is not a great bar. What seems to be 
needed is that in the event of a fatal explosion the 
coroner of the district should be enabled to write to the 
Home Office for scientific assistance in arriving at the 
originating cause. The Secretary of State might then 
call upon any competent engineer for a report on the 
matter, when he could be examined as a witness before 
the jury. The mere knowledge that any explosion would 
be strictly investigated. by an expert, might, in many cases, 
be sufficient to counterbalance the too prevalent tendency 
to prefer risk to expense. 

The Hydbaulio Test, 
Although, as we have seen, the application of a known 
amount of hydraulic pressure is in such general use for 
the determination of the strength of a boiler, there are, 
nevertheless, few points in engineering about the real 
value of which there is so much dispute. Everybody 
seems to have a different opinion on the matter. Some 
€ay that the hydraulic test is the only means of determin- 
ing the strength of a boiler ; others that it is a very in- 
jurious and useless measure. As to its amount, some 
recommend one-and-a-half, many twice, some thrice, and 
a few «ven four times, the working pressure. While 
numerous engineers advise its application to old boilers, 
others have strong objections to its use in this way. 
Whether the force-pump be really the best apparatus for 
its application, is, with other questions, also placed in 
doubt. The truth is that, while on the one hand, like 
other tests, it may be abused and wrongly applied, on the 
other its value may also be exaggerated. 

The best practical proof of its necessity for new boilers 
is afforded by the fact that explosions have occurred the 
first time steam has been got up — such as that at the 
Atlas Works, Manchester, in 1858. Unless every plate 
be separately tested up to proof load, it is impossible to 
be certain whether one of them is not defective. This 
function is clearly much better performed by the hydraulic 
test. Then, as to its application to old boilers, much can 
be learnt during internal examination, but it is not always 
possible to tell the remaining thickness of the plates by 
this meatis, nor their deterioration through the heat. It 
is often said that a successful resistance to the hydraulic 
test is no proof that the boiler might not have been 
burst hy a few pounds more; and that it may so 
iuffer as to perhaps afterwards burst with a 
less pressure of steam. But this is no more true 
than it is true of a girder, for instance, which 
has withstood without permanent deflection its proof 
load. In every case it is necessary that its effects on 
the boiler should be exactly ascertained. In fact, the real 
test consists in this examination, and the proof pressure is 
only a nieans to this end. The boiler should, if possible, 
be subjected to a careful internal and external examina- 
tion. With locomotives this can only be accomplished by 
taking out the tubes ; with ordinary land boilers it can only 
be done by removing the brickwork. In fact, it may be said 

that a steam boiler is never absolutely safe which cannot 
be easily examined — more especially from the inside. 
But by gauging the flue tubes, the combustion chambers, 
the flat surfaces, and even the barrels, it may be ascertained 
very nearly whether the limits of elasticity of the material 
have been exceeded — whether therefore the pressure has 
additionally injured a boiler which was near rupture al- 
ready. It is often very plausibly observed that there is great 
danger in testing a boiler, which cannot be examined in- 
ternally, to double, or even to only one and a half the work- 
ing pressure. It is said that the test may strain the 
boiler without its showing any outward indication. 
It is certainly just possible that such a case might 
happen. A locomotive toiler, which had been tested with 
1961b8. pressure, the water being at 162° F., in Septem- 
ber, 1860, but had not been examined internally, burst on 
the 1st of April, 1861,* under only 1201bs. of steam. 
The boiler gave way at the smoke-box ring of the barrel, 
and, as usual, from a furrow or crack running close 
to and parallel with the inside overlap of the longi- 
tudinal joinf. It is difficult to believe that if this ring, 
as well as the others, had been gauged after stripping 
the lagging from the outside, as is done by the engineers of 
the Manchester Boiler Association, it would not have shown 
a permanent increase of diameter or some bulging under 
the extra pressure. If, in addition to a neglect of careful 
measurements before and after the application of the 
pressure, this test is carried very high, then the whol& 
operation may undoubtedly be a cause of that which it is 
intended to prevent. According to the Prussian law, 
every new locomotive boiler had to be re-tested to double 
the working pressure after running 8,000 Prussian miles, 
and afterwards for each 5,400 miles. These measures, 
while they did not entirely prevent explosions, greatly 
injured the boilers, by straining the staybolts, and 
by the resulting excessive caulking required to make 
the joints tight. On the other hand, the absolute 
security afforded by drawing the tubes can, under tho 
present mode of construction, be only obtained at tho 
expense of, perhaps, 300 tubes, costing from 25s. to 27s, 
each, besides some injury to the tube plates. 

Wliatever may be said against the hydraulic test, the 
best argument in its favour is its very general adoption* 
New Government boilers in the United States must be tried 
to a pressure two-thirds greater than the working pressure j 
the same measure being carried out with the 3,000 boilers 
in the city of New York. Mr. Anderson, C.E., of Wool- 
wich ,f directs his subordinates to use a test of at least 
double the working pressure for the boilers in the royal 
gun factories. Mr. Muntz, of Birmingham, has publicly 
stated that he has for years adopted an annual hydraulic 
test, "considering it a duty he owes to his workmen." 
The Eastern Counties, the South Eastern, the Lancashire 
and Yorkshire, the Caledonian, the North British, the 
Edinburgh and Glasgow, and the London and South 
Western Railway Companies employ the hydraulic test 
for both new and old boilers, using generally double the 
working pressure. The London and North Western are 
stated to have used it for only new boilers — at any rate, until 
recently. The Great Northern and the Great Western 
Railway Companies do not use it, and it is accordingly on 
on these lines that the greater number of explosions take 
place. Practical experience thus proves that, though 
there is just a chance of the test failing to detect a weak 
boiler when it cannot be examined internally, the danger 
is greater in not using the hydraulic test at all. Mr. Beattie, 
of the London and South Western, strips the lagging 
every two years, and applies a pressure of 190 lbs., the 
working pressure being 125 lbs. Mr. Fletcher, of tho 
Manchester Boiler Association, employs double the in- 
tended working pressure for new, and from 1 J to If the 
worjiing pressure with old, boilers. The most commonly 

* Board of Trade Report. 1861. Part 4. 
t " Instructions to be Observed in the Management of Steam 
Boilers in the Royal Gun Factories." 



used test is thus double the working pressure for old 
boilers, with a diminutioQ according to ch'cumstances as 
they get old. 

An objectionable plan in measuring the pressure applied, 
and, for several reasons, one likely to lead into error, is 
estimating it from the load on the safety valve lever. A 
metallic gauge should be used, and very neat pocket 
instruments of the kind are sold in Paris. In frosty 
weather the rivet heads are liable to be snapped if the 
metal be not somewhat warmed by using hot water. The 
hydraulic ram kind of action on the sides is also much 
less likely to occur if a rather narrow force pipe be used 
for the pump. 

There can be no doubt tha! it would be a valuable 
thing to be able to employ some means of measuring the 
permanent and the temporary extension of volume, if 
any, produced by the hydraulic test. It is probable that a 
boiler, as it gets old, and takes a permanent set under the 
pressure, also increases in volume ; so that it doubtless 
holds a few gallons more that it did when new. 
An ingenious plan for measuring the increase of 
volume is recommended in the Bavarian regulation. 
After the boiler is filled, the amount of water 
forced in is measured by pumping it from a vessel 
marked with divisions. When the pressure is removed 
the boiler contracts more or less, forcing out at least a 
portion of the water ; the amount remaining is supposed 
to give the dilatation of volume of the boiler. The diffi- 
•culty in the use of this plan would probably consist in the 
presence of air in the water itself, and any which might 
chance to remain in the boiler. That in the water might 
be greatly diminished, or at any rate brought down to a 
constant amount, by boiling ; but there would be no pre- 
cise security against any air in the boiler, and as the 
weight of the air absorbed by water (according to a well- 
known law) is in proportion to the pressure, it would be 
taken up by the water, thus falsifying the indications when 
the pressure was removed. On the other hand, a high 
temperature of the water would form an impediment to 
this absorption. The experiment is certainly worth trying. 
It might be very valuable with tubular boilers inac- 
cessible from the inside, as any permanent set or de- 
flection ought to be indicated by little or no water 
being compressed out by the contraction of the boiler 
on the removal of the pressure. As long ago as 
1844, M. Jobard, of Brussels, in order to obviate the 
supposed injurious effects of the hydraulic blow of the 
water on the plates, proposed to fill the boiler with water, 
first loading the safety valves, and to then dilate the 
water, and consequently the boiler, by means of heat 
-applied to the outside.* More recently. Dr. Joule, of 
Manchester, has used the same plan himself, proposing 
it for general ad option. f In addition to the loaded safety 
valve, he used a metallic pressure gauge " to be constantly 
observed, and if the pressure arising from the expansion of 
the water goes on increasing continuously without sudden 
decrease or stoppage until the testing pressure is 
obtained, it may be inferred that the boiler has sus- 
tained it without having suffered strain." Another 
plan, also founded upon the same principle of the irre- 
gularities of extension of metals when the limit of 
•elasticity is exceeded, has lately been proposed. J This 
consists in bringing an ordinary steam-engine indicator in 
communication with the pump plunger as if it were a 
steam-engine piston-rod. The ordinates of tlie pencil 
diagram would thus give the pressure in the boiler, while 
the respective abscissae would give the quantity of 
water pumped in at each stroke. As long as the limit of 
elasticity was not exceeded there would be a horizontal 
line, while a curved line would appear as soon as the 
sides began to take a permanent deflection. There seems 

* " TechaoloRiste," 1844. p. 135. 

t '* On a Method of Testing the Strength of Boilers." 
Joornal of the Manchester Philosophical Society, 1862, 
p. 97. 

I Polytechnisches Centralblatt, p. 1,337, 13 October, 1864. 

to be a sort of contradiction in depending for results like 
these upon such irregular appearances as the extensions 
beyond the elastic limit. But all these proposals are 
undoubtedly worth trial in practice. Dr. Joule's plan has 
the merit of affecting the plates by both heat and pressure — 
thus bringing them under every-day conditions. 


Mr. Lewis Olriok said there were some points in the 
paper with which he did not agree. It was stated by 
Mr. Paget that one cause of injury to steam boilers was 
the percussive action of the steam when suddenly cut off 
by the slide valve, which caused a recoil upon the sides of 
the boiler. On this point he would remark that, in the 
great majority of boilers used in England, the slide valve 
did not suddenly cut off the steam ; in most cases the 
slide valve was moved by an eccentric, and the cutting off 
was gradual, and not sudden, as in the case of the Ame- 
rican engines ; and this remark, therefore, only applied to 
those engines where the expansioir gear acted suddenly. 
Allusion had been made to the straining of the cylinder 
covers. He had seen such cases, and he had also observed 
the foundation- plate give at each stroke of the 
engine; but he had no doubt, if Mr. Paget had 
examined the plates in such cases, he would have 
found that this was not caused by the percussive 
action of the steam, but was owing to an insufficient 
amount of metal and insufficient strength put into the 
proper place. He had noticed this in the case of an 
engine of 20 horse-power, which had been in use for many 
years in the factory of Messrs. Maudslay, where there was 
an insufficiency of metal in the proper place. He had 
never seen it where the cylinder covers were strong enough 
for the work they were expected to do. Another point 
mentioned by Mr. Paget was, that the steam room in the 
boiler should be proportionate to the size of the cylinder ; 
he should have been glad if Mr. Paget had stated what 
he considered to be the proper proportions. Reference had 
been made to the caulking of boilers under pressure. 
This might be done when a boiler was tried by the 
hydraulic test, but the proper way was to take off the 
pressure, and then caulk and put on the pressure again. It 
was only the question of a minute to pump the pressure 
up again, and a few strokes more gave the additional 
pressure, beyond the former one indicated by the chalk 
mark. The next point he would allude to was with 
regard to the feed water. In would appear that many 
engineers did not consider it wrong to insert the feed 
water pipe near the fire box. Quite recently he had seen 
that done in the case of a locomotive, in which a Giffard's " 
injector was employed ; and he would call the attention 
of those who had not considered the subject to the ex- 
planations which Mr. Paget had given as to the injurious 
action of the feed water on the boiler plates. The next 
point in the paper had reference to the superior heat- 
conducting power of thin boiler plates as compared with 
thick. This was no doubt the case, but in speaking of 
the American plates, Mr. Paget had omitted to mention 
the superior quality of those plates, which made it 
possible to use them of a thickness which would not be 
ventured upon in England. Within the last few years 
the quality of the best plates in this country had almost 
come up to the American standard, but those generally 
used were not so good. Allusion had been made to 
the voltaic action that took place in steam boilers, and 
the evils that might follow from it. Some years ago a 
pamphlet was published by Mr. Zerah Colburn, in which, 
the action of steam-boiler explosions was explained, anidi 
the question of the galvanic action was based upon the high 
authority of Professor Fai-aday, to which he (Mr. Olrick) 
would willingly bow. He entirely agreed with the geaierai 
remarks in the paper with respect to explosions. They 
involved the sacrifice of a great amount of life and» pro- 
perty, and he thought it would be desirafel» for the 
Government to take this matter la hand,, and. to ia- 



troduoe stringent rules to make people more careful 
with their boilers. The greatest amount of mischief 
was occasioned by employing men to attend to boilers 
who knew nothing whatever of the properties of 
the steam-engine. It was a question which could not 
be too much impressed upon people, that there should be 
proper periodical inspections of boilers, according to the 
system adopted by the Manchester Association. Mr. 
Paget had mentioned the hydraulic test. There was a 
great difference of opinion amongst engineers on that 
question, but no doubt, as Mr. Paget had pointed out, 
practical experience led to the conclusion that in all cases 
where this test was carefully applied there were much 
fewer explosions than where it was neglected. The 
cases of locomotive engine explosions had occurred solely 
on lines where that test was not employed. On the sub- 
ject of the wear and tear of steam boilers he would 
remark that the great cause was defined by the 
single word •'neglect," often on the part of the designer 
and manufacturer. When a boiler was made too small 
there must be forced firing, and the consequence of that 
was early destruction of the boiler. A further deteriorating 
cause waa defective circulation, producing similar conse- 
qaenoes. There was one point which it was almost un- 
necessary to mention, viz., that if boilers were not properly 
stayed they would give way earlier than if proper atten- 
tion was paid to the staying. But the great evil arose 
after the boilers came into the hands of the owners, from 
employing unskilled persons to work them. The amount 
flaved in wages in this respect was an injudicious economy, 
and it was a question whether parties who confided boilers 
to such people ought not to be made responsible in a 
<50urt of justice in the event of explosions taking place. 
Amongst the various evils to which steam boilers 
were exposed there was none worse than bad feed 
water, which was a frequent cause of their destruc- 
tion. A most grievous evil was scale in the boiler, 
which lowered the heating power, and thus it was most 
important that it should be frequently removed. Scaling 
arose from bad water, but as rain water was not generally 
to be procured, they had to be satisfied with well water, 
which was generally very hard, and which led to large 
•deposits of sulphate of lime in the boiler. For the re- 
moval of the carbonate of lime from the feed water, he 
Jbelieved Dr. Clark's process was very effective, though the 
means by which the result was accomplished would ap- 
pear strange to those unacquainted with the subject. 
Lime was added in excess, which caused the precipitation 
>of the salts of lime already in solution, and thus the 
water was purified.* There was also another plan, which 
had been successful in preventing scale, known as Martin's 
invention, which he had no doubt was also efficient. In 
.that plan the feed water was made to pass through a 
<5ylinder containing plates arranged diagonally and tilled 
with superheated steam; the water deposited its scale 
upon these plates before entering the boiler. The con- 
sequence of this was a clean boiler instead of the accumu- 
lation of scale. The usual way of removing scale was 
sending boys with hammers into the boilers and knocking 
it otf, which often caused great injury to the structure 
-of the boiler, from carelessness in the operation. He was 
^ure they must all feel indebted to Mr. Paget for his 
valuable and exhaustive paper. 

Mr. Stensos remarked that mention was made in the 
paper of the circumstance of the stay bars in boilers being 
in a crystalline state, and only requiring a slight blow of 
a hammer to break them. He had heard papers read 
before this and other societies in which this question had 
been debated, but there was one point which required 
first to be settled — viz., the real condition ©f the iron 
previous to its being made into stays. AVas it crystalline 
before it was so used? or had it become so by use? He 
had been connected with engineering the greater part ot* 
his life, and he must say he had never met with 

♦ Journal of the Society of Arts, vol. iv., p. 424j 

an instance in which it was satisfactorily proved 
that the iron had been converted from its fibrous 
condition before use. It was asserted that percus- 
sive action tended to produce a crystalline condition 
of the iron. This might be so, but he required further, 
proof of it. He had cut up and examined a great many 
piston-rods and connecting-rods of locomotive engines 
working at great volocity ; he had found them to be in 
various states — some partly crystalline and some entirely 
so, while others had remained fibrous throughout ; and 
he had found the same characteristics of inequality in the 
tires of railway wheels. The leakage of boilers had been 
referred to in the paper, and he held it to be a very 
important subject for investigation. He knew, from 
experience with boilers in his own use, that a very small 
leakage would destroy the plate from the outside. The 
oxydation commenced at the spot, not where the water 
leaked, but where it evaporated and the plate was dry. 
The destruction of the plate from this cause was so rapid 
that he had known a f -inch plate cut through by a small 
leakage in a few months after the boiler was put up. He had 
no doubt this was caused by the chemical action of the water 
upon the plate. With regard to scale, Mr. Olrick had meur 
tioned a plan which he regarded as efficient in preventing 
the usual effects of the deposition of carbonate and other 
salts of lime in steam boilers. There could be no doubt ' 
of the destructive effects of those deposits upon the 
plates of the boiler, as also of the retardation thus 
caused to the heat. He should be glad to hear some 
further explanation of Mr. Martin's process, as he 
regarded scale as the greatest element of destruction 
with which they had to contend in the working of steam 

Mr. Adams, whilst agreeing to a great extent with 
what had been stated in the paper, took exception to the 
remark that the method of welding plates reduced their 
strength. He had seen many successful experiments in 
welding, by Bertram's process, at Woolwich, and it was 
invariably found, under ordinary circumstances, that the 
weld was the strongest part of the plate, for it was a well- 
known fact that a piece of iron forged after it came from the 
rollers was stronger than when it left the rollers. Mr. Paget 
had quoted from some German authorities respecting the 
temperature at which water was decomposed, but he would 
state a practical fact within his own experience. On one 
occasion the steam was allowed to stand stagnant in a super- 
heater for ten days, and on the tenth day the metal of the 
superheater ran away into the fire, but no decomposition of 
the water had taken place. With regard to the hydraulic 
testing of boilers, engineers were not agreed as to whether 
the testing should be made at a high temperature or not. 
They knew, in testing a boiler cold, they had the friction 
of the rivets ; but in hot testing the expansion of the 
metal bv heat caused a great difference. The rivets 
expanded to a greater extent than the plate itself, because 
the expansion of the rivets was longitudinal and along 
the fibre, whereas the expansion of the plate was across 
the fibre and not so great, and the power which the friction 
of the rivets gave to the strength of the plate would be 
less when cold ; but to oppose that there was the greater 
strength of the plate due to the low temperature. Mr. 
Adams then, by means of a diagram, described in detail 
Martin's process for preventing incrustation in boilers. 

Mr. G. F. Wilson, F.R.S., on the subject mentioned 
in the paper as to water or steam in contact with iron 
being decomposed, would give an instance in his omiQX^ 
perience where such was not the case at a very high 
temperature. It had come under his observation that 
steam passing day by day through iron pipes at a i;ed 
heat was not decomposed, or there was no evidence of its 
decomposition. The theory was that hydrogen ought to 
have been formed and an explosive mixture should have 
been generated, but practically such explosive compound 
was not formed. , x xu 

Mr. Olrick wished to add, witl^ reference to tue 
hydraulic testing of boilers, that he had in many in- 



stances used hot water for the test up to 200 degrees, as 
by that means the boiler was brought into a very similar 
state to what it would be in when at full work. 

The Chairman said it now became his duty to move 
that the thanks of the meeting be given to Mr. Paget for 
the paper with which he had favoured them. It was very 
comprehensive in its scope, and he thought contained 
many valuable suggestions. No doubt public safety was 
of the first importance in matters of this kind, and the 
mode in which that could be best obtained seemed to be 
practically indicated by the inspections undertaken by 
the Manchester Society. Other means no doubt might 
be taken for ensuring tlie safety of the public ; but there 
was no plan so effective as when the public took care of 
itself, as was the case at Manchester. With regard to 
the economy of wear and tea:*, it was a question for en- 
gineers, and one upon which lie could not venture to give 
an opinion ; but, undoubtedly, it was an important ques- 
tion for those who employed sream boilers in their manu- 
factories in which a large amount of capital was invested. 
They must all feel indebted to Mr. Paget for his careful 
investigation of the subject, and the able manner in 
which he had treated it in his paper. 

The vote of thanks having been passed, 

Mr. Paget, in acknowledging the compliment, said that 
a perusal of his paper would show that he had very care- 
fully guarded himself from stating that any impulsive 
action on the sides of the boiler could be brought to bear 
by means of the gradual action of the side-valve. In 
speaking of the effect of galvanism on steam boilers, he of 
course only meant the chemical action on the plates pro- 
ducing wear and tear, and therefore the primary ruptures 
leading to explosions. With respect to incrustations, he 
thought that the effects they produced were simply those 
which ensued whenever a plate got red hot. In speaking 
of the charcoal plates used in America, he was necessarily 
aware of their superiority to iron made with pit-coal. 
Testing boilers by means of hot water instead of cold, 
was often, as he stated, very advantageous, and, in- 
deed, necessary. With regard to the crystallization 
of iron, and with respect to Mr. Stenson's remarks, 
he thought that this state was simply due to strains 
in excess of the elastic limit, abstracting elasticity and 
ductility, and therefore inducing brittleness. The 
crystallized appearance of a surface of fracture was 
simply due to the mode of fracture. His observa- 
tions with regard to Bertram's joints were founded on 
the results of experiments conducted at Woolwich for 
the Admiralty. With respect to boiler insurance com- 
panies, their action undoubtedly offered the best means of 
safety and economy; at the same time, their future 
spread needed some extraneous stimulus, more especially 
in sparsely populated districts, like the agricultural and 
some of the mining counties. 

The Natal Court attracted great attraction at the Ex- 
hibition in 1862, from its wild and picturesque objects of 
native industry and spoi-ts of the chase, and it will be 
equally well represented at Dublin this year. From an 
interesting local account, the following particulars are 
taken : — 

First comes the interesting collection so opportunely con- 
tributed by Mr. Barry. That gentieman has recently 
returned from his long and devious trip across the conti- 
nent, and some of the curiosities which he has gathered 
together during his journeyings are new and rare. These 
articles are very illustrative of domestic life among the 
Bechuana tribes of the interior, and especially so of the 
people living around Lake Ngami. We doubt whether 
such a gigantic pair of bullock horns has ever been sub- 
mitted to British eyes as that presented to Mr. Barry by 
Lechulatabe, Chief of the Batoana. They are certainly 
second only to the monster pair in the first Inter- 

national Exhibition. Several pairs of rare buckhoms^ 
are also contributed by Mr. Gifford, Mr. Baker, aiid* 
Mr. Topham. The gemsbok horns, lent by the first? 
of these gentlemen, are, from their size, very interesting.. 
To the same class belong the skins of various antelbpes 
and animals. The poisoned arrows belonged to Bush- 
men, and are made of dwarf reeds pointed with bone spines,, 
thickly covered with the deadly poison obtained from a 
small beetle which infests a tree of the mimosa tribe. The 
are sticks found in the same sheath as the arrows are the 
roughest mode of ignition known. The upper stick has- 
to be twisted in its charred socket for about ten minutes, 
before the sparks are created. Some caps and head-dresses, 
made of feathers and skins and worn by the Bechuanas 
near the Great Lake, show how the barbaric ideas of cos- 
tume advance as we go northward. They are principally 
worn on frosty nights — for in the winter months of the 
mid-year the cold around the marshy borders of the lake 
is severe. Among other domestic accessories picked up by 
Mr. Barry are some rattles, made of large seed pods; a 
fan, formed from the tails of golden 'jackals, and which 
are also used for the purposes to which pocket-handker- 
chiefs are generally applied ; some spoons and ladles, 
cunningly carved in twisted shapes, from solid pieces of 
wood. There are also some articles in this part of the 
collection valuable in a commercial sense. The fibres are 
very fully represented, both in their raw state and in^ 
various kinds of twine, cord, and thick rope, made and 
used by the natives round the Botlellie river. These 
fibres are mostly obtained from different varieties of marsh 
grass, and the rope exhibited has been employed in the 
trapping of elephants and the capture of hippopotami. A 
hundred yards of very strong fishing netting, as used in^ 
the waters of Ngami, show how large and valuable are 
the fibre resources of all Southern Africa. The tribe from 
which these specimens were got is the Bajeye or Bakoba. 
Reference should be made to the large earthenware jars,, 
which, as superior specimens of native pottery, well deserve 
inspection. In this lot will be found a war knife, with an 
oddly-carved shaft. This comes from a tribe living to> 
the south of the Zambesi, and never yet visited by a whito^ 
man. Perhaps the most grotesque object is the rudely 
carved elephant, a primitive specimen of sculpture. These 
are the principal items in Mr. Barry's contribution, which 
is likely to be the best assortment of African curiosities 
in the Exhibition. 

There are, however, other more local representatives of 
native industry. Mr. Tophara*s valuable collection com- 
prises the entire range of Zulu Kafir economy. The 
hard, grim looking logs of stained wood are the pillow 
and stools which form almost the only furniture in the 
native's hive-like hut. The little snuff-spoons, with their 
long prongs for insertion into the woolly wig adorning the^ 
manly brows of the savage, are no mere ornament, but,, 
in consort with the snuff-boxes, made out of small gourds- 
and calabashes, are in constant use every hour of the day.- 
Nor is the office of the stone pipe a sinecure. This per- 
haps represents the most primitive form of narghileh. 
Seated in a circle, this calumet is passed from hand to- 
hand, until the enchanted smokers subside into a wakeful 
stupor, caused by the strong fumes of the dacca or native 
hemp, whose smoke is inhaled through the water at the 
bottom of the cow-horn. Some idea of native aptitudes- 
for mat- making and basket-work will be gathered from 
the specimens shown. That the natives are not devoid of 
the artistic faculty, a glance at some pieces of bead-work 
will show. Since it became compulsory on natives to 
enter the limits of townships clothed, the demand for 
beads has not been so great. Fashions regarding them 
vary very much. Sometimes large red ones will be in 
vogue, at other times small speckled ones. It is at their 
kraals, however, on state weeding occasions, that the 
Zulus may be seen to the greatest advantage in their 
panoply of beads, feathers, skins, and other savage finery- 
There is also a bundle of Amaxosa assegais, and a very 
interesting Bushman spade, sent by Col. Maclean. The 



prmer are as suggestive in their way as the spears dis- 
played ia the Tower, while the last, it must be re- 
membered, is the industrial handiwork of a race which 
ranks lowest in the scale of humanity. Periiaps, how- 
ever, the most remarkable of all these native curiosities is 
the gigantic and very striking piece of wood-carving ex- 
hibited by Mr. Horwood, and obtained by him from the 
native who made it in Zululand. This strange object 
consists of three graduated central bowls of carved wood, 
stained black, and diminishing in size as they rise up- 
ward. All around them smaller bowls project, and each 
has its basin-like cap. The height of the whole structure, 
— for it really deserves that name — is nearly five feet, and 
its diameter about three feet. It is entirely hewn and 
cut from one solid block of wood, and it took the maker, 
who had only a knife to work with, eighteeen months to 
execute. Its use is to hold beer. Old African travellers 
say that they have never seen anything at all equal to 
this extraordinary production. 

The most valuable part of the collection is that which 
illustrates the industrial and commercial resources of the 
colony itself. But allowance must be made for the hurried 
nature of the effort. The articles that are exhibited have 
been hastily got together, and they must by no means be 
taken as a pattern sample of what Natal can grow. In 
regard to sugar, which may be looked upon as the staple 
product, there is a sample of the best yet made in Natal 
by the ordinary process. It comes from the estate of Mr. 
H. Shire, on the Umhlanga, and was made in his battery 
by Mr. Collard, a Mauritian sugar- boiler of great experir 
ence. In size and purity of grain, it almost equals sugar 
made by the vacuum pan process. The vacuum pan 
sugars from Canonby estate are sui generis. No other 
plantation yet possesses this important appliance. Alto- 
gether the array of sugars will be enough to prove that 
Natal is equal, as a sugar-producing country, to either the 
Mauritius or the West Indies. Mr. A. Wilkinson's 
display of rum, rectified spirits, and rum shrub will be a 
new feature never exhibited before. The spirit is manu- 
factured from the refuse of cane crops, and is fit for 
chemical purposes or varnish. 

Mr. Baker shows samples of wool and angora hair well 
prepared, and there are also fine samples clipped from the 
flocks of Mr. Mesham and Mr. Tomline. 

The Cotton Company's bales of cotton are better 
samples than those shown in 1862. Mr. T. Reynolds 
sends a beautiful parcel of cotton from Oaklands. Mr. 
Martin's hank of wild cotton twist, from near Delagoa 
Bay, and the sheet made therefrom, may afford some 
speculation to those interested in the discovery of new 
fibres. The very fine samples of flax from Messrs. C. 
Hunter and Co.'s flax-works ought to attract some notice 
in Ireland, where this staple gives support to so many 
people. Mr. Beningfield's aloe and pineapple fibres show 
to what purpose two plants — one of which is met with 
wild while the other grows like a weed — can be put. In 
Mexico, the Indians and the halfcastes dress largely in 
fabrics made of the agabe. There are hosts of fibres little 
known to the scientific or industrial world, but very 
valuable withal, existing in a wild state in this colony and 
the interior. Dr. Mann's collection of woods is complete 
so far as it goes, 'though nece?sarily not so numerous as in 
1862. Mr. Topham also sends some beautifully pre- 
pared woods, many of which take a fine polish. No 
better-flavoured tobacco can be desired than that of Mr. 
O. Manning. Rich, mild, and fragrant, it is just what a 
critical smoker would desire. Mr. Hodgkin also sends 
colonial cigars. Cayenne pepper is abundantly repre- 
presented from samples from Mr. P. Steel, Mr. J. P. 
Voysey, and Mr. Russell. All, however, differ in colour 
and quality. There need be no limit to the local pro- 
duction of this article — the pulverised capsule borne by 
the chili and capsicum bushes. Arrowroot is only repre- 
sented by a sample from Mr. Stainbank, the last season's 
supply having benn all shipped. 

Corn is not so fully or fairly represented as could be 

wished. Messrs. Henderson and Sjott's wheat proves 
however what can be done in that wiy, and Mr. Baker's 
oats are equally as significant ; but of the great item of 
maize — the staple corn stuff of the country — there is only 
one sample. Mr. Topham has also sent a piece of copper, 
mined and smelted by the natives. Coals have not been 
overlooked, Mr. Baker having forwarded a box of superior 
specimens. These will go to show that the Coal Com- 
pany has something tangible to support its designation. 
The local smiths never hesitate in giving the preference 
to colonial over imported coal — the former burns so long, so 
bright, and so well. 

Mr. P. B. Short has contributed luscious and tempting 
conserves of pine-apple, bananas, and araatungulu. The 
last-named, being a native fruit, will be new to those who 
look at it. The syrups made from the same fruit, and 
from the pineapples, have golden and delicate pink tints 
that are very pleasant to the eye. The copies of Messrs. 
Davis and Son's Naval Almanacs are a creditable example 
of our literary and typographical capabilities ; and the 
maps sent by Dr. Mann will assist the spectator to form 
an intelligent comprehension of the colony from which 
these articles have come. Messrs. Brock have promised 
some of their excellent photographs; but Dr. Mann*s 
photographs of Bishop Colenso's " intelligent Zulu " and 
his wife, will excite as much interest as any other item on 
the list. 


The Belgian Minister of the Interior has addressed the 
following circular to the governors of the various pro- 
vinces : — 

**M. LE GouvERNEUE, — A Universal Exhibition of the 
products of agriculture and industry and the fine arts is 
to open at Paris on the 1st of May, 1867. A Commis- 
sion, presided over by his Imperial Highness Prince 
Napoleon, has been charged with its preparation and 
direction. By request of the French Government, a 
committee has been now instituted in Belgium to place 
itself in communication with the Imperial Commission, in 
order to furnish it with the information it may require 
respecting our country, and bring before it the wishes of 
our manufacturers. 

" This committee consists of M. Fortamps, Senator, 
formerly Chairman of the Belgian Committee at the 
London Universal Exhibition, President; M. Adam, 
Director-General of Direct Contributions, Customs, and 
Excise; M. Bellefroid, Director-General of Agriculture 
and Industry ; M. Romberg, Honorary Director-General 
of Fine Arts; M. Moxhet, Director of the Consulates; 
M. Kindt, Inspector of Industry, Members ; MM. Dulieu 
and Clerfeyt, Secretaries. 

" The committee is authorised to place itself directly in 
connection with you, as well as with the Chambera of 
Commerce, Commissions of Agriculture, and other com- 
petent bodies, for everything concerning the mission with 
which it is charged. 

" Be kind enough, M. le Gouverneur, to give the com- 
mittee the assistance it requires to accomplish its task, 
and to allow it to find the same willing aid among the 
authorities to which it may have to address itself. 

" Everything appears to indicate that the Universal 
Exhibition of 1867 will have an exceptional importance 
and brilliancy. The development recent Customs reforms 
have given to the commercial relations of France and 
Belgium, already previously considerable, and the exten- 
sion these relations may still receive for the advantageof 
the two countries, permit us to suppose that our producers 
will endeavour to occupy a distinguished place, worthy 
of their renown, and conformable to their interests. 

" In any case, as it is important that we should have a 
sufficient notion of the amount of space which should be 
reserved for the products of our fellow-subjects in the 
Exhibition building it is intended to construct, I request 
that you will take what you consider the most efficient 



means of ascertaioing the requirements of those persons 
in your province principally interested in the Exhibition 
of 1867. If you cannot yet obtain precise information as 
to the exact space our exhibitors will require, you will at 
any rate be able to procure general indications as to their 
probable participation in the coming Exhibition, and thus 
to furnish me with those elements without which the in- 
terests of our countrymen might not be sufficiently 

" I request you, M. le Gouverneur, to omit no pains to 
obtain the most exact information, and to place yourself 
for that purpose directly in communication with the compe- 
tent authorities and the chief manufacturers of your pro- 
vince. I ask your zealous assistance in this matter, and, 
as the affair is urgent, pray you to acquaint me with the 
result of your inquiries with the least possible delay. 
(Signed) "A. Vandenpeereboom, 

Minister of the Interior." 

iiu ^rts. 

Paris Exhibition. — The annual exhibition of Fine 
Arts opens, as usual, in the Palais de I'lndnstrie, in the 
Champs Elysees, on Monday, the 1st of May, and the 
collection is expected to be beyond the average in quality, 
as it will certainly be in quantity. The weather just now 
is magnificent, and those who can spare the time for a trip 
to Paris in May, or the first half of June, will have a fair 
chance of seeing the city in its gayest aspect, besides 
having the opportunity of studying the results of French 
art on a large scale, and at their ease, for the size of the 
building and the enclosed garden, in which the sculpture 
is always admirably exhibited in the midst of green lawn 
and glowing flowers, supply together one of the finest 
places for such a purpose in Europe. 

Photograph op Dante. — The portrait of Dante 
painted by Giotto in a fresco in the chapel of the prison 
of the Bargello, in which the immortal poet was once 
incarcerated, is well known to the artistic world, but the 
engravings of the work give but a very poor idea of it. 
A photographer has recently succeeded in obtaining an 
admirable reproduction of it, which is about to be pub 
lished in five different sizes, from that of a carte de visite 
to half that of the original. 

telegraphic purposes, and the only objection to its use is 
the evolution of some suphuretted hydrogen, which 
would seem to be unavoidable. In the course of his 
experiments the author arrived at the following conclu- 
sions : — 1. That finely-divided sulphur in contact with the 
electro-negative metal of a pile formed of zinc, copper, 
and solution of common salt notably increased the electro- 
motive force, constancy, and permanency of the battery^ 
and he hopes to obtain by the use of sulphur a voltaic 
combination possessing many advantages over the batterica 
at present employed. 2. Sulphur, although insoluble and 
an insulator, enters into combination with the sodium set 
free by the current. It remains for the author to explain 
the action of the small quantity of sulphide of copper 
which is formed, and which appears to be essential. For 
this end he has undertaken further experiments. 

^ — — 

Tuscany Straw Work. — It appears by an official 
report that the annual value of this industry is about half 
a million sterling. The soil of Tuscany is said to be the 
only kind in Italy which will produce straw of sufficient 
fineness for the purpose, and it is only in the immediate 
neighbourhood of Florence itself that the highest quality 
can be produced. The farmers of the Romagna, the 
Marches, and of Naples, have often attempted to grow it, 
but have never completely succeeded. The straw in 
question is that of a peculiar kind of wheat, which never 
attains more than fourteen or fifteen inches in height, and 
bears very few grains of corn. The sewing together of 
the plats is as nice an operation as the platting itself, and 
each requires great practice and infinite patience. More 
than half a million of straw bonnets are made each year 
in Florence. In certain localities, such, for instance, as 
Empoli, 4,000 or more women are employed in the trade ; 
Sesto has about half that number. 

Galvanic Pile. — At a recent meeting of the Academy 
of Sciences, M. Matteucci read a paper ** On the Action of 
Sulphur in the Galvanic Pile." The author has expe 
rimented on the battery recently introduced by M. Blanc, 
who employs a plate of zinc and a plate of lead covered 
with a very thin deposit of copper, which are placed in a 
solution of common salt, with which is mixed a quantity 
of sulphur. This battery appears to be very useful for 


The Stagnation op Commerce. — Messrs. T ravers 
and Son, in their circular, say : — '* Probably at no previous 
period has there ever been a more general stagnation of 
commerce than at the present moment. Instances have 
been known of more severe depression in this and other 
countries, but none in which the limitation of business 
was so universally observed in all parts of the world. In 
the United States the imports of the past six months 
have scarcely been more than a fifth of those of the cor- 
responding months of last year ; in India the suspension 
of transactions is reported by the most recent telegrams 
to be almost complete. From -China the accounts are 
equally discouraging, while in South America, AustValia, 
&c., although the markets are less flat than elsewhere, 
there is no particular activity. Of course the brunt of 
this great change will have to be sustained by England ; 
but our manufacturing and producing power is so exten- 
sive and varied that we have more capability than other 
nations of sustaining ourselves under exceptional circum- 
stances. Hence, although the evidences of the contrac- 
tion of trade are seen among us on all sides, they are less- 
apparent here than in France, where the unprecedentedly 
rapid accumulation of the stock of bullion is aconsequenee 
of the reduced demand for money for commercial pur- 
poses. At the beginning of the year it was a question in 
this country, whether the diminution in the commercial 
demand for money, would so far counteract the effects of 
the requirements for our headlong commitments to 
foreign loans and undertakings, as to allow a decline of 
the rate of discount to 6 per cent. ; but it is plain that 
the extent of tlie impending revulsion was then under- 
estimated, and now that the slackness in our industry has^ 
been aggravated by circumstances taking place in the 
iron trade, which have caused large orders to be sent ta 
Belgium, the prospects seems to be that the rate may 
remain for some time at the present point, even if it 
should not temporarily go below it." 



Colonial Societies. — A movement has been originated 
in Victoria for the establishment of a Society of Arts, 
Manufactures and Commerce, the objects of which are to 
be the encouragement of arts and manufactures in this 
colony by disseminating information thereon, and by 
bestowing pecuniary and honorary rewards for such produc- 
tions, inventions, and improvements in this department, and 
the introduction of new industries, as tend to promote emu- 
lation, economy, and consumption, more extended employ- 
ment, increase of social enjoyments, of trade and 
commerce, and of national wealth. A similar society is 
suggested in the Hobarton papers for the colony of 
Tasmania, which has already done much good through 
its Royal Society, MechanicsVInstitutes, Agricultural and 
Horticultural Societies. 



AooLiMATisATioN IN VICTORIA. — At a meeting of the 
'OouDcil of the Acclimatisation Society of this colony, a 
letter was read from J. A. Youl. declining to undertake 
the shipment of another lot of salmon ova, and stating 
"that he has for* various reasons been obliged to decline a 
:0imilar request made by the Tasmanian salmon commis- 
sioners. A letter was read from Mr. 11. Philpott, giving 
80me further particulars about the shipment of Angora 
goats, and advising that, if possible, a further sum of 
money should be sent home for the purchase of these 
animals. Dr. Black mentioned that it was at his sug- 
gestion the Council had determined to import some of the 
Angora goats, convinced as he was that there was no 
animal more worthy of the exertions of the society, or 
one that would redound more to their credit to establish 
there. After a conversation as to what amount should be 
set apart for this purpose, it was unanimously determined 
to devote a further sum of £900 for the introduction of 
Angora goats, thus doubling the amount already in Mr. 
Philpott's hands. A letter was read from Mr. Layard, 
of Colombo, stating that he had sent three axis deer and 
one Ceylon elk. (These have arrived in good condition.) 
lietters were also read from California, stating that seven 
^f the Californian mountain quail had been received at 
the Botanical Gardens, and that the Sambur deer had 
•arrived safely at Yallock ; and speaking in sanguine ternts 
•of these fine animals soon penetrating into the Streletzski 
-Banges, and becoming established there. The secretary 
•reported that he had received two tortoises and two 
-ostrich eggs from Mr. J. Mackie, who brought them from 
ihe Cape. Mr. Mackie states that it is now quite a 
-common thing for the farmers to have a flock of ostriches 
in a state of semi-captivity, and that a very large profit 
is derived by the sale of the feathers. Mr. Mackie thinks 
that the eggs might without much difficulty be brought 
io this country and hatched, where he has no doubt the 
breeds would thrive and do well. They were to be col- 
lected together at the Exhibition building between the 
Ist and 10th of March, and the whole despatched by 
*he Oreat Britain^ which was to sail on the 1 6th of that 
month. The board appointed to promote the objects 
•of the present undertaking have availed themselves of 
*he experience of Mr. J. G. Knight, the secretary to the 
commissioners for this colony at the London Exhibition 
in 1862, in the executive management of the matter. 


Danish Industrial Exhibition. — The Danish papers 
-contain intelligence that the Government has resolved to 
hold an industrial and artistic exhibition at Copenhagen in 
1866. A committee has been formed lor the purpose, 
ijonsisting of twenty- five members, presided over by the 
<^rown Prince Frederick. Thecliairman of the committee 
is Councillor Forchhammer. The exiiibition is to be 
opened on the Ist June, 1866, in the ridmg-house of the 
Castle of Christianborg, and will include raw stuflis, as 
well as manufactured goods and objects of art. 

Hydraulic Works in the Doubs. — A very important 
work is about to be undertaken in tlie ilcpartment of the 
Doubs, in France, with the object of economising and 
regulating the waters of the lakes of Saint Point and 
fiemoray, and of improving the rivei- Doubs from the 
lake of Saint Point to thH point where tlie Doubs empties 
itself into the S&one. The actual level of the lakes is 
to be lowered, two hundred acres of marshy land re- 
claimed, and the drainage of the entire neighbourhood 
re-arranged ; finally the lakes will be deepened, so as to 
increase and regulate the water power, which is used by 
ninety factories of various kinds on the Doubs. The 
cost is estimated at £96,000, but the value to the existing 
factories is set down at £24,000, and it is expected that 
alarge number of new works will spring up in consequence 
of the improvements to be made. 

AirrooBAPHio Telegraph.— It is officially announced 
that the new telegraph, which heretofore only operated 
between Paris and Lyons, will be opened to the public, on 
the 1st of May, between the former city and Havre. 

Gas Lighting in Paris. — The consumption of gas in 
Palis has doubled in the eight years from 1857 to 1864. 
The Compagnie Paiisienne d'Eclairage sold, in 1857, 
1,979,134,379 cubic feet, and in 1861, 3,870,600,105 cubic 
feet, about half the total quantity supplied. There are 
about 687 miles of mains only. There is a good market 
for th" coke, and the aramoniacal sold for £5,121. The 
Paris Company, in order to induce the sale of their coke, 
make and sell at cost price a stove specially adapted for 
burniuij this material in houses and shops, and of these 
stoves they sold no less than 2,755 in the year 1864; the 
total number in use at the end of that year was 11,291. 

Lenoir Gas Engine. — There weie, on the 3l8t of last 
December, no less tiian 143 of these ingenious, simple, 
and compact little engines working in Paris to the satis- 
faction of those who employ them. 


CiT7 Horticulture. — Sir, — As city horticulture is 
by no means confined to flower sliows, so neither is window 
gardening restricted to pots of flowers, or to appliances 
to be added after the houses are built. If window 
gardening be a pleasant and cheerful thing why should 
it not be provided for in the first instance by architects in 
their designs, and by builders in their structures? By the 
provision for the indulgence of this taste thus becoming a 
forethought instead of an afterthought, not only would 
greater capacity be obtained in the receptacles for these 
miniature /ar^rres, but greater elegance and more harmony 
with the elevations of the buildings. Indeed, it may 
fairly be hoped that improved arrangements for the 
gratification of this taste may lead to new architectural 
features of much beauty. For instance, the sills of 
windows are sometimes made to continue the string 
courses running along the frontage; that is, often the 
string courses run immediately below the windows. If, 
therefore, the receptacles of these miniature gardens project 
somewhat, immediately at the base of the windows, and 
they are ornamented with patterns, why should not these 
patterns be continued on the string course? If these 
receptacles be in iron, they might be painted terra cotta. 
colour and the rest of the string course be supplied in terra 
cotta to match, or if porcelain or encaustic tiles face the 
window gardens, why may tlicse not also be continued in 
tlie same fashion on the remainder of the string course? 
Supposing two or three rows of windows on a house or row 
of houses thus decorated with dilferent agreeable patterns 
running along the jstringcouisesanii window-gardens, they 
would surely have a pleasing ellect? If a builder, in 
constructing a row of houses, say, for the artizan class, 
were thus to fit up and decorate each alternate house with 
window-gardens, leaving each alternate one plain, I fancy 
he would find tliat the former would go off his hands 
l)efore the others. And I would submit- the suggestion 
that a prenjium for such designs of liouse elevations, com- 
bining window gardens in jdeasing liarmony with archi- 
tecture, might legitimately appear in the Society's prize 
list for next year. We frequently hear complainte of 
want of novelty in architecture, and provision as above 
for the indulgence of the taste for fljwer-growing, in 
union with architecture, in this most nature-loving me- 
tropolis, woull afford one fieature of originality which 
would really belong to us. — I am, &c., John Bell. 

Photography on Painting Canvas. — Sir, — Will you 
kindly correct an error which occurs in your journal of 
the 2 Ist inst. On page 380 credit is given to the Belgians 
for having devised a successful method of printing by 
means of photography on painters' canvas. The method 
referred to is my process with collodio-chloride of silver, 
described at a' recent meeting of the Photographic 



Society. I desciibed its application to painters' canvas 
in the FhotograjpMc News, on Februarj' 10th. The article 
in whch 1 described it was translated into a Belgian 
journal, and duly acknowledged ; from thence it was 
transferred into a French journal, quoted as from the 
Belgian journal, the acknowledgment of the original 
source, doubtless inadvertently, being omitted. This is 
probably the origin of the error. By correcting it you 
will much oblige, yours, &c., G. Wharton Simpson. 



Hon. ...Entomological, 7. 

British Architects, 8. Annual Meeting.^ 
Asiatic, 8. 

Rojal Inst., 2. Annual Meeting. 
Tubs. ...Societj of Arts, 8. Cantor Lectures. Dr. F. Grace Cal- 
vert, " On some of the Most Important Chemical Disco- 
veries made within the last two years." (Lecture IV.) " 
Civil Engineers, 8. Mr. Callcott Reilly, " On Uniform 

Stress in Girder Work." (Part II.) 
Royal Inst., 4. Prof. Frankland, " On Organic Chemistry." 
..Society of Arts, 8. Mr. William Stones, " On Colonisa- 
tion ; its Aspects and Results." 
R. Society of Literature, 8^. 
THUKS...Royal, 8^. 

Antiquaries, 8. 

Linnsean, 8. 

Chemical, 8. 

R. Society Club, 6. 

Artists and Amateurs, 8. 

Royal Inst., 4. Prof. Frankland, " On Organic Chemistry.' 

Fri Philological, 8. 

Royal Inst., 8. Professor Henry Fawcett, " On Wealth and 

those who produce it." 
Archaeological Inst., 4. 
Sat Royal Inst., 4. Prof. Bain, "On the Physical Accompa- 
niments of Mind." 


From Commissioners of Patents Journal, April 21 «^ 

Grants op Provisional Protection. 
Air engine (compressed)— 818— A. B. Baron Von Rathen. 
Alumina, sulphate of— 900— A. A. CroU. 
Boots and shoes, feet protectorsjto he used loose in — 908— J. Poole and 

T. Brown. 
Buildings, construction of— 822— J. TaU. 
Buttons— 1007— G. Davies. 
Cartridge boxes— 902— A. V. Newton. 

Centrifugal force, rinsing and drying by— 604— H. A. Bonneville. 
Coal, machinery for mining— 558 — G. Lauder. 
Coflfee, substitute for— 979— M. Diosy. 
Cornice rings, manufacture of— 977— C. H. Williams. 
Cornices, ventilation by perforated tubular— 813— T. H. Saunders. 
Drying wool, cotton, &c., system of— 255— E. T. Hughes. 
Engines, governors or regulators for— 991— S. Smith & J. W. Jackson. 
Engines, traction— 962— J. G. N. Alleyne. 
Fabrics, dyeing and printing— 804— A. Paraf. 
Fibrous substances, machinery for carding— 983— J. Ellis, C.Walker, 

and W. Preston. 
Fibrous substances, preparation of— 948— A. and H. Illingworth. 
FJles, machinery for cutting— 1013— T. Tuiton. 
Fire, apparatus for giving alarm in case of— 267— M. Cartwright. 
Fire-arms— 969— C. W. Lancaster. 
Fire-arms, breech loading— 987— A. Muir. 
Forks, cleansing jind polishing of— 950— C. Martin. 
Gas, regulating the supply of— 972— C. Esplin.' 
Gr in, apparatusforthreshing,&c.— 742— J.Marshall. 
Hammock, portable covered— 894— T. W. Nordenfelt. 
Hay, straw, &c., machines for cutting— 934— R. R. Riches and C. J 

Heat er cold, preventing the transmission of— 864— F. Le Roy. 
Inking rollers, manufacture of— 914— A. V. Newton. 
Iron ships, &c., protecting from oxidation— 970— E. Ritherdon. 
Kitchen ranges — 940 — F. Brown. 
Lamps, reflectors for — 897— B. Baugh. 

Lighthouses, apparatus for illuminating— 945— J. R. Wigham. 
Locks— 999— N. G. Kimberley. 
Looms— 928— A. W. Pearce. 

Matches, &c., frame filling machines for— 1003— H. J. Simlick. 
Motive power, apparatus for obtaining— 3140— W. A. Turner and T. 

T. Coughin. 
Musical instruments, stringing and tuning— 954— W. Moody and W. 

J. Huband. 
Nut crackers, &c., handles of— 993— T. White. 
Oil and grease, lubricating— 966— W. Teall, L. Lepaige, and E. T. 

Ornamenting metal tubes, machinery for— 924— G. Burt. 

Photograph! cameras— 1009— V. A. Prout. 

Photographic images, production of— 712— R. A. Brooman. 

Postage stamps, &c., manufacture of— 936— J. H. Johnson. 

Projectiles and cartridges — 932 — J. vender Poppenburg. 

Railway breaks— 745— H. A. Bonneville. 

Railway carriages, Ac, stopping or retarding— 1021*-G. Voigt. 

Railway trains, communication between the guard and passe^igers of 

— 858-H. J. Walduck. 
Railway trains, communication between the passengers and guard of 

—929— J. C. Stovin. 
Safes, construction of— 904 — T. Cook. 
Safes, manufacture of— 585— S. Chatwood. 
Safes, securing the doors of— 946— G. C. Thompson. 
Sewing— 848— E. H. Smith. 
Sewing machines, binding attachments for— 601— H. E. Clifton and 

A. HoflFnung. 
Shaping machines— 896— W. M. Neilson. 
Shot, shell, .cc, rounding and polishing— 952— W. Clark. 
Sizing paper— 1005— W. Weatherley. 
Soda and potash, manufacture of— 1011— A. G. Hunter. 
Steam boilers— 906— J., D., B., and O. Swarbrick. 
Steam cultivation— 956— W. Bulstrode. 
Straw, apparatus for reducing- 985— R. Garrett, jun. 
Telegraphic apparatus— 910— H. A. Bonneville. 
Toast racks, manufacture of— 811— J. Burley and L. Glover. 
Vegetable materials, separating fibre from— 958— G. T. Bousfield. 
Washing machines— 605— H. A. Bonneville. 
Weights, safety tackle for raising— 937— P. J. Jamet. 
Yarns or threads, machinery for finishing— 1019— R. Fergusson and 

W. Ralston. 

Inventions with Complete Specifications Filed. 
Mineral oils, lamps for burning— 1040— C. Boschan, J. Bindtner, an 

W. Caflfou. 
Vessels, connecting a gaff to the mast of— 1067— C. R. Fisher. 

Patents Sealed. 








G. Hartley. 

J. Shaw. 

G. Davis. 

J. E. A. Gwynne. 

C. H.Gardner ii C. English. 

A. Muir. 

W. O. Walbrook. 

E. E. Colley. 

J. Smith. 

J. W. Scott. 

H. Bateman and E. G. Gar- 

G. T. Bousfield. 

J. Heap and T. Jolley. 

J. and R. Cunningham, 

P. A. le Comte de Fon- 

J. Walmsley and N. G. 

J. and H. Charlton, and 
J. O. Christian. 

E. Pilkington. 










C. W. Wardle and R. Mcln- 

H. B. Harris & J. P. Thom- 

T. N. Kirkham, V. F. En- 
som, and H. Brook. 

J. R. Crompton. 

D. Ellis and M. Hillas. 
A. Field. 

W. B. Adams. 

J. H. Johnson. 

A. D. Hall. 

W. Bardwell. 

J. and W. Thornton. 

M. Benson. 

E. Beanes and C.W.FinzeU 
E. Williams. 

J. Hewes. 

W. B. Newbery. 

J. G. JN. Alleyne. 

C. V. and A. 0. Walker. 

From Commissioners qf Patents Journal, April 25th, 
Patents Sealed. 
A. Reynolds. 

H. E. Craven & T. Carrack 
J. Tate 

J. Dannatt. 

B. F. BruneL 
F. Jenner. 

C. May. 

J. Stobo and W. Pollock. 
W. Congalton. 

D. Laidlaw and J. Robert- 

W. Cormack. 
A. and W. t^mith. 
J. H. Simpson. 
C. O. Crosby. 

E. Edwards. 
J. F. Brinjes. 
W. Aston. 

2729. J. Dodge. 
2735. H. A. (i Wynne. 
2753. G. Simpson. 
2777. S. Rydbeck. 
2789. J. Robinson & J. Gresham. 
28U6. G. Smith. 
2825. H. W. Ripley. 
2831. G. Bell aid R. Luthy. 
2863. W. E. Newton. 
2979. A. V. Newton. 
3028. W. E. Newton. 
3174. W. Reid. 
3238. J. H. Johnson. 
96. J. G. Jones. 

165. J. A. Shipton and R 

332. C. Beard. 

Patents on which the Stamp Duty of £50 has been PAm. 

1044. J. F. Mathias. 
1201. F. Dangerfield. 
1152. J. Combe. 
1165. C. C. Creeke. 
1294. T. F. Griffiths. 
1218. A. C. Kirk. 

1190. C. E. Heinke. 
1235. G. Bischof,jun. 
1461. A. Nicole. 
1199. J. F. Allen. 
1210. R. C. Mansell. 
1215. J. Shaw. 

Patents on which the Stamp Duty of £100 has been paid. 

856. M. Rowan & T. R. Horton. ( 875. W. H. F. Talbot. 

876. J. Horsey. 925. E. Hunt and H. D. Pochin. 

903. C. Lungley. J 978. L. Talabot.